Forgive for being naive and the length of this post, but I’m a beginner (I’ve had the game for about a week). I absolutely love TBS games and this game is awesome, but I’ve been having ‘Map Locations’ issues on the first campaign mission, Homecoming”. I can’t seem to get the different map locations straight. Some locations like chests and stashes of a resource like wood or sulfur disappear after a hero opens it, Other locations like mines (gold, ore, sulfur...etc.) offer a specific resource on a per day basis. But once a hero visits, a red flag appears and it now says “owned by red player”. Does that mean if another hero visits he/she gets nothing? Well, sometimes I visited said mine with another hero and received more resource. Other times, I got nothing...what the hell? Some locations offer resources, but just once a week, so I’m assuming that means if another hero visits that same location in the same week, he/she gets nada! Then there are the locations like the “Tree of Knowledge” that offers a ‘1 level up’ to any hero that visits once and only once. OMG, I am so confused. Why am I posting this? Because I realize how precious resources are, but also know so are movements on the map. So far every time I’ve tried this mission, I waste so many movements visiting locations and getting nothing. I’ve checked every guide out there and not one of them are specific. They’ll tell ya what the location offers, but not to what heroe(s) and how often.
Now I know if someone answers this post, there’s a good chance I’m gonna get something like this, “Dude, stop bitchin’ and just play the game. The more you play, the more experience you’ll get and eventually you’ll get the hang of it”.
And that’s a fair comment (except for the Dude part). But here’s my point - there are a gazillion guides out there for HOMM3. A lot of them offer a ridiculous amount of detailed info on everything like combat numbers on every unit type at every level from every town type. Nobody’s gonna read that. So here’s my challenge: A list containing every location type (for now just the Homecoming mission) with detailed info. 1) What heroes can visit, 2) How often can they visit 3) What is offered either one or more of - a skill, a spell, gold, experience...etc., 4) If the location offers a resource, for what duration.
BTW, this info should only address all locations that heroes ‘could’ visit, not necessarily ‘should’ visit
IMHO, this information would help beginners like me get off to good start moreso than just about anything else.

First, please put the title of the game earlier in the post. Ideally, it should be in the topic subject line, so that readers know which game to expect before they even open your thread. You did tell us, but it was buried down in the post. I guessed which game based on game objects before I reached the answer.

Second, be glad you are playing Heroes 3 instead of Heroes 2. One of the small but pervasive quality-of-life improvements in Heroes 3 is that the game now indirectly answers many of your questions in the status text when you hover over a location. In some cases, you need to have visited a location once to unlock that hint text, but once unlocked, it remains. For example, once you visit a once-a-week site, the status text will include "(already visited)" when you hover, as a reminder that you should not go again. In contrast, in Heroes 2, it was the player's responsibility to remember which sites had been visited this week.

Have you looked at HoMM.com's Map Locations page? It doesn't directly answer some of your questions here, but it's still a useful resource. It can be visited as many times as you like, unlike some in-game locations. ;)

Now, to your questions:

Mines (which include Sawmills and Alchemist's Labs) give a specific amount of resource to their owning player at the start of each day. If no one owns the mine, no one benefits from it. There is no resource value in sending any of your heroes to a mine that you own. (You might send a hero there to garrison it, but that is a separate topic.) If an enemy hero owns a mine, you should send a hero to it to take ownership of it so that its resources go to you, not to your enemy. If the enemy did not post a garrison, any hero, no matter how ill-equipped, can capture it. Some people will encourage you to hire a secondary hero whose sole purpose is to capture any combat-free resources and mines, so that your combat-oriented hero can focus on fighting and visiting hero-specific sites.

Some sites, such as Mystical Gardens, Windmills, and Waterwheels, give their resource to the first player who visits them in a given week. You can use any hero you own to visit them, so again, if the area is not contested, use a secondary hero. No more than one player per week can benefit, so if your enemy gets there first, wait until Day 1 to visit. If you have visited it with one hero, there is no point in visiting again with another in the same week.

Sorry, I don't know Homecoming well enough to help you with specific advice about that map. However, HoMM.com does have a page discussing the campaigns, which provides high-level walkthroughs. I usually just play random maps in skirmish mode. I will reiterate that you should always check the status text when you hover a location. If you've been there before, the status text will hint to you about how you should handle subsequent visits.

Advowson is correct on pretty much all points. I'll add that if you right click (and hold) on a site, then you'll also get a little pop up with similar information and maybe a little extra description.

Generally speaking, mines don't need to be revisited as long as you own them; they'll add the relevant amount of their resource to their owner's stockpile each day. If it isn't yours, then you should probably visit it to claim it.

Piles of a resource (like gold or gems), treasure chests, and artifacts are one-time things, and they will disappear from the map after being used. Resources are added to your stockpile, while the hero collecting the chest or artifact will be the one getting the experience (if you choose experience) or holding the artifact. Artifacts are automatically equipped if the hero has an open slot for that type of artifact, otherwise the artifact goes into the hero's backpack.

Sites that give a permanent boost to a hero (ex. Star Axis, Learning Stone) will boost each hero exactly once for that map. Ex. Once Fiona has received the bonus from visiting a given Learning Stone, she'll never get anything else from that learning stone even if another player hires her and sends her to visit it, but she can still visit other Learning Stones for a bonus.

Sites that give a temporary boost to a hero (ex. Oasis) generally last until the next battle. Some exceptions include the Stables, which lasts until the next week starts (so visit it early in the week to get the most effect), and the Mana Vortex in the Dungeon town (sets the hero's current mana to twice their current max). If the site gives a temp bonus, then it usually says how long that bonus lasts.

Some sites like the skeletal adventurer or the abandoned wagon will either be empty for the entire map or will give a few resources or minor artifact to the first hero to visit them. They won't disappear, but they never expire or refill either. After you've seen them be visited (whether by you or someone else), then they'll be marked as "visited" and you shouldn't waste your time going back.

Creature dwellings (including refugee camps) will refill their population at the beginning of each week. You'll need to send a hero over to hire the creatures each week if you want those creatures; if you don't care to buy the creatures, then don't bother visiting the site if the structure is flying your flag. It is worth at least flagging the structures, since each dwelling will boost the population growth of the relevant creature by 1 in all towns with the building that are owned by that player. For example, each Centaur Stable you control on the Adventure Map will cause all of your towns with a Centaur Stable to produce 1 extra centaur each week.

Some buildings provide a small number of resources to the first player to visit them each week. Examples include Windmills, Watermills, and Mystic Gardens. Only the first player to visit gets anything, and if no one visits during a given week, then no one gets the resources for that week.

Just check the manual. Mines and resources are summed up in one simple paragraph. It reveals the terminology to be "resource mines" and "loose resources".

The manual is in the same folder as the game, and named:
Heroes3_Manual.pdf

There are two other manuals for the expansions, however this manual is where it all begins.

On page 2 is the "Table of Contents". The key word there would be "Adventure Map" and that is shown to begin on page 13 and end before page 23.

If you just want to know only about mines and resources, then I think you will find the final paragraph on page 17 sums it up rather nicely. It has the heading "Resource Mines and Loose Resources" in large bolded letters.

Thank you for your awesome post and I want to thank all of you on this page for taking the time to answer my locations questions. Each of you provided excellent clarifications. Dummy me never tried right-clicking on a location. No question, I have to pay more attention to all the info on screen. I can’t tell ya how many times I’ll be playing some game cursing up and down and screaming something like, “How am I supposed to know how much MP I have”, or “Where the hell is the objective marker”? My son would say “Dad, it’s right there in the lower right corner.” (Yup, I can be that lame)

Anyway, sorry for not posting the title (see, I wasn’t paying attention...I thought all the posts in this section were for just HOMM3). I just finished the second mission, “Guardian Angels” and was victorious on the first try. And I gotta tell ya, all of your responses were a huge help. For example, In “Homecoming”, the main issue that I had was I didn’t realize that the resource locations I captured (a red flag showing my ownership), could be then be captured back by an enemy hero. OMG, thanks to you guys in “Guardian Angels”, I now noticed that that some of these locations now said, “owned by tan player”).” Hey scumbag, getcha hands off my stash. No problem, send a hero, get it back. I had ten heroes running around and I didn’t waste one move the whole mission. And BTW, this mission was so cool. New towns, new creatures, great stuff! Wizards and witches and necroes, oh my. I can’t get enough of this game.

I think you (any of you) should consider making a quick quide on map locations. I’m tellin’ ya, it would help beginners like me more than anything else relating to this game. So again, huge thanks. I hope you all realize that you’re special people. Why? Because you’re GAMERS!!!

The campaigns and later missions in a campaign tend to have fewer restrictions, as well.

Something to keep in mind, because it isn't obvious and is a common mistake: after you complete a campaign, you'll be offered a chance to save. Do so (perhaps in a separate slot). When you want to start another one of the campaigns, then LOAD THAT SAVE. Don't just click "New -> Campaign", unless you want to start the entire set of campaigns from scratch. If you see a little golden check mark on each campaign you've completed, then you did it right.

By the way, you can leave creatures to guard a mine. To do so, simply reenter a mine that you own, or if you're already standing on top of it, press Space.

Keep in mind though, that this might not always be the best idea, since when those creatures are attacked, they will be in battle without a hero's support. Meaning they won't have access to spells and won't get bonus to their attack/defense from the hero.

While yes, this CAN be done, I'm hard pressed to come up with a situation where it is the appropriate response. If a mine is important enough (and at risk enough) to guard that way, then it is important enough to also assign a hero to do the guarding. A hero will be able to respond to a changing situation, and the hero can do other things with those guards if the mine is safe.

Actually, this might be a good time to ask: ZFR, have you ever had a situation where placing guards in a mine was useful? I think I've done it once or twice just for the novelty, but otherwise I'll park creatures in the nearest town or non-combat hero if I don't want to haul the creatures around.

Never. And after making this post I did start to think about it and came to the same conclusion. If a mine is super important to guard, it's probably better to hire a level 1 hero, put him there and let him sleep. At the very least, he'll add his attributes and cast spells in combat. And more importantly, the creatures won't be stranded; he'd be able to move about and do other stuff while protecting the mine.

I had one game where I assigned guards to a mine, not because I wanted them to guard it, but because I didn't want to dismiss that creature stack and needed the all spaces on all the nearby heroes for more important units. The mine ended up serving as a temporary way station for orphaned monsters until I could get a transport hero to come by and retrieve them. There were no enemies nearby, so I was confident that the monsters would not get attacked.

The one other use case I can see for guardian monsters is to protect mines from a wandering scout hero (one with a tiny army that can be vanquished by almost anything). I've never actually had a game where the enemy obliged me by sending such an underequipped hero, though.

Actually, this got me thinking. Were you ever in a situation where you willingly put creatures in a garrison gate?

Hm. I don't think so, for pretty much the same reasons that I don't put creatures in a mine. If it is worth guarding, then it is worth using a hero to do it.

The only exception was mentioned above, where I use the gates more as a dumping point for some excess creatures than to actually guard the location (like dropping a small stack of imps to free up a slot if I don't have a convenient way to convey them back to a town), and even then I'm more likely to use them as retaliation eating cannon fodder.

There are the maps where you own some garrisons that are pre-stocked, but I pull the creatures out of those and add them to my army if possible.

Playing campaign maps I have put small stacks of random monsters there nothing other good to do with in gates just to see enemy hero's army going through.