- Make sure the tutorial messages are enabled in the settings, and actually read them when they do pop up in game. They don't necessarily explain everything, but they do generally relay pretty good info.
- Lots of graphical elements of the game (not strictly limited to UI elements) have tooltips that pop up on hovering your cursor. Make use of the context and information these provide.

- I don't know that the tutorial mentions it, but there's a button near the speed controls that lets you turn on one or both of two different info overlays for the city. I would strongly recommend using the setting that shows both zombie density and resources & survivors. It's vital to be able to identify, at a glance, hot spots where dangerous amounts of zed have accumulated (green = relatively few, yellow = starting to become dangerous, etc.), and the ability to see recruitable survivors and scavenge-able food and other resources right on the map is also really useful.

- Even though the old browser games were exclusively turn-based, and Rebuild 3 can be played that way, I recommend using real-time mode. Since jobs can take fractional days, and turn-based mode just advances 1 full day at a time, you'll wind up wasting a lot of your survivors' time that could better be put toward them completing subsequent assignments. Note that you can pause at will and assign new missions, reassign equipment, etc., while paused. (In real-time mode, the space bar toggles between pause and whatever speed setting you had set for normal time advancement.)

- If you do play in real-time, pause frequently. Seriously. Any time you get one or more notifications on the right side of the screen indicating that some task was completed, I recommend pausing to read/clear them all, and then assigning the now-idle survivors who had been working on those tasks to new missions (or to other survivors' still-ongoing missions, if you think they might need help).
Note that survivors' default state is "guarding", represented by a shield icon; always be on the lookout for this, as there are few legitimate reasons you should need to have people actively assigned to guard a spot, other than awaiting an imminent attack from one or more nearby hordes of zed or enemy raiders, of course. Try to make sure all survivors are always doing something useful.

- As you should've learned from the tutorial, your main "hero" survivor is the only one that can level up in any skill just by doing; the others only "learn by doing" for their class' relevant skill (e.g., defense for soldiers). Consequently, aside from the fact that members of a given class are likely to be better at doing that's class' jobs than other people will be, you should avoid assigning survivors to tasks that some other class could gain skill from -- especially if you actually have a member of that other class doing something else unrelated. (Note that scouting isn't affected by any skill, and I don't think it trains any skill, either. EDIT: I was partly wrong: scouting missions do seem to train the scavenging skill at least a little. But as far as I can tell, that skill doesn't affect the outcome of a scouting mission whatsoever -- scouting always reveals everything about the block(s) in question, and I'm pretty sure always takes 1 full day, regardless of the scout's class or skills.)
However, don't worry too much about class-correct job assignments in the very early game, when you'll likely need everyone to contribute to zombie killing at some point, for example.

- Zed spawn in the city over time, and they spawn faster in blocks immediately bordering your fort (blocks that only diagonally touch one of your reclaimed blocks don't count as bordering). Your chosen difficulty setting determines both the starting zombie amounts and the rate of further accumulation. (And certain types of buildings might accumulate zed faster or slower, or even not at all.) Also, no new zed will accumulate on any block which has a mission active on it.
One of your main priorities should be keeping the outside of your walls relatively clear of zed. It's a lot more time-efficient (and safer in the long run) to try to keep adjoining blocks from ever getting to yellow density than it is to either defend against or assault the massed zed that will eventually spawn as result of doing too little clearing.

- Scouting is another thing you need to keep on top of, as unscouted locations are horribly dangerous and likely a waste of time to kill zombies or scavenge in, and impossible to reclaim. Beyond the hopefully obvious strategy of "don't leave blocks that are or will soon be adjacent to your fort unscouted", I try to prioritize scouting blocks that are immediately adjacent to any block I could theoretically clear and reclaim right now (basically, two blocks out from my walls in every direction). One of the only scouting priorities I would routinely place above the scouting of that second-tier buffer around your fort is scouting immediately outside the walls of another faction's fort. The computer-controlled factions don't play by the same rules the player has to play by, and can claim even heavily zed-infested blocks. They also don't scavenge like the player does, but any survivors or resources in a block that gets reclaimed by another faction will still be lost to you, and unless you're roleplaying heavily as an altruist, there's usually little reason not to try to recruit and scavenge as much as you can from just outside their forts' walls before those blocks wind up inside their walls.
Also, as mentioned above, scouting can be done equally well by any survivor, so -- early on, at least -- you might as well use whomever is least needed for other stuff at the moment...which, in the early game, can often mean your engineers and leaders (if you have any).

- Pay attention to the danger rating of any mission outside the fort. Unless you're in the early game on one of the highest difficulties, you should avoid sending your people on a mission with a yellow danger rating, and pretty much never let a mission with an orange or red danger rating go off. Either add more people until it's safer, or wait, maybe looking for other ways to decrease the danger in the meantime. (There are some mission types, like scouting or reclaiming buildings, which, if they're allowed, are always safe -- barring random events that always have a chance of occurring.)

- Keeping tabs on both your amount of stored food and your "food flow" is important. You can see what your average per-day gain or loss in food is at any time. As long as there's plenty of food available to scavenge, and at least a couple scavengers to bring it in, a slightly negative food flow (like maybe -2 per day) is okay. Of course, this depends on how much food you currently have: -3 food/day will be okay for a while if you have 50 stored food, while -0.5 food/day with only 5 food in storage is pretty bad.
Note that you can assign people to actively farm, fish or hunt to supplement you farms' passive production, but scavenging should usually be preferred, as long as there's still plenty of scavenge-able food on the map; after all, many locations have both food and other resources, which can net you valuable weapons and other equipment, as well as medicine, fuel, and -- more essentially -- materials and ammo.
Avoid actively recruiting more survivors if your food stores are low-ish and your production negative (unless you're pretty sure you'll be able to turn the food situation around very soon thereafter).

- In the early game, scavenging is probably going to provide a majority of your food income, as well as valuable resources and equipment. Always try to scavenge buildings before reclaiming them, as (IIRC) you get less of whatever was there if you wait to scavenge a building till after it's in your fort. However, avoid scavenging food if you're at or near your max food storage amount, as any overage will be lost. (If possible, avoid even getting to that point by trading away however much food you feel comfortable with, if you realize you're bringing in more food than you need or can store. Better to trade for other resources or equipment you don't currently need -- but for which there's no storage limit, unlike food, and which can potentially be used for barter in future transactions -- than to just let the food go to waste.)

- Recruiting can be a tricky business. You obviously need to keep an eye on your housing capacity, but you also need to avoid causing your food flow to go too far negative for too long by over-recruiting and having no plan to reverse that additional loss of food.
Note that most (not all) recruitment events with different possible responses have the same outcome for a given response every time, and it's often what you might reasonably guess (no, trying to grab the gun of that paranoid person would not be a great idea). The problem is that a lot of the better options require a certain leadership level, and some require that your fort have certain amenities. You just need to weigh how badly you need the person right now against how okay you are with them starting out with lower happiness (if you lied to get them to come with you) or having a recurring illness (if you took in a sick person without first curing them with a medkit), as a couple examples. Happily, there are very few active recruitment events that don't allow you to leave and come back later...though even some that allow this have a hidden timer which, if it elapses, might cause you to miss your chance.

- (Try to) always be reclaiming (or building). Any block adjacent to your fort that's completely free of zed is a candidate for reclamation. Better to have your survivors work on reclaiming a cleared block you don't particularly need right now than wait until later, when it'll have to be cleared of zombies again. And remember, new zed will not accumulate on a block for as long as a mission is active on it. So even if you wind up cancelling a reclamation task, it will still have kept zed from moving back into that building while the work was ongoing.
Avoid spending materials and your builders' time building structures within your fort that you could easily reclaim from without. That is, if a type of structure that you want or need exists within two or three blocks of your walls, work toward getting there instead -- especially if it's the sort of structure you normally only need one of, like a lab or a school.
Don't destroy useful structures to build others unless you're in a city type that has way more than you could ever need of some (like farms) and none, or nearly none, of others (like workshops). Even then, it would still be better to prioritize useless or nearly useless blocks (like fields) for conversion to other things.
Unless you need a building built in a hurry (or have a shortage of builders), try to demolish structures first, then build new. The materials gained from demolition will mostly or entirely offset the materials used for the new building.

- Equip any useful gear you get as soon as you can. Don't be afraid to shuffle gear around as you obtain new stuff to enhance survivors' class skills, or give them an edge in something that they don't technically need, but which can help (like boosting their defense for scavenging or recruiting missions in uncleared areas of town).

- The most crucial "uncommon" structure you should try to find and reclaim is a laboratory (which looks like a nuclear power plant for some reason). Getting one, and getting your engineers, if any, working on research will pretty quickly make your life easier.
Among the many useful inventions and improvements which can be unlocked is the ability to craft zombie traps (in a workshop, which is another less common structure to try to get) that you can place on specific blocks and which will slowly decrease the number of regular zed there, then keep it zed-free until such time as the block is reclaimed (or the trap is destroyed by a mobile group of enemies) -- all without tying up your soldiers. And if you do reclaim a block with a zombie trap on it, you can redeploy that trap elsewhere!
Also, the main way to increase your food storage cap is by researching certain agriculture-related things in the lab. (The other main way is by reclaiming warehouses, which are fairly rare structures which you have no way to build. In other words, under no circumstances should you EVER demolish or convert a warehouse.)
One of the earliest things you can research is called "survivor management", which allows you to (sooner or later) talk to people and learn about their backgrounds, as well as see their relationships with each other. The most immediate benefit is that you'll be able to choose perks for your non-hero survivors who've attained certain skill thresholds in their class. In aggregate, these perks can have a significant impact on the effectiveness, survivability and happiness of your people. Also, the ability to see some info about people's relationships (positive or negative) can help you avoid putting incompatible people together on assignments (which can cause problems in the long run).

- A hospital should also be very high on the list of less-common structures to reclaim or build as soon as you reasonably can. As long as you don't have one, any injuries your people sustain will take longer to recover from, and there are certain events that will have a better outcome if you own a hospital, too.

- Survivor happiness is less important to worry about than zombies and food, but it's still something you want to check on from time to time. Once you've got enough people and farms that your zombie and food problems are not as pressing, it's probably a good idea to periodically sort your survivor list by happiness, scroll to the bottom, and assign anyone whose happiness is below, say, 25-30% to rest (or, in the case of anyone who's currently on a non-indefinite assignment, at least make a mental note to give them time off as soon as they're done). Just make sure to check those on vacation periodically, too, so you don't have people just chilling for weeks after hitting 100% happiness.

- Any two survivors in your fort will, if they are assigned to missions together for long enough, eventually form either positive or negative opinions of one another -- there's no such thing as a long-term neutral opinion in this game. These opinions are always both mutual, and equal in intensity. (In other words, there will never be a case of Person A liking Person B, who dislikes Person A; nor will the degree of like or dislike differ between the two.) The more time they spend sharing the same assignment, the stronger this mutual feeling will become. People getting to work with friends tend to get occasional bonuses to their happiness (and, in this game, immediate family members and spouses are always considered to be something like good friends); forcing people to work with their enemies for long enough might cause unpleasant events to occur.
(Unfortunately, the dev decided to present this relationship info in one of the more unhelpful ways I can imagine, only allowing you to see the three currently-strongest relationships for each survivor (with spouse and family always presented ahead of any other relationships), rather than, say, allowing you to see all of the people they dislike, all their family, etc. It got to the point where I decided to start keeping a simple log for each town recording who dislikes whom, outside the game, which I update every so often. I wouldn't advise anyone else to worry about this, though, unless you get to a point where your survivors' negative relationships are causing problems in your settlement.)