I love Necropolis, but I must be doing it wrong. The skeletons are incredibly weak at the start, and by the time zombies hit anything, it's had time to go off, start a family, and send its grandkids back to fight. The wraiths are okay but not outstanding. That's what I think so far anyway. I have played a bunch of times, but always found the start very hard on Necropolis.
How do you guys start somewhat strong?
Do you have any rules of thumb for when to upgrade regular skeletons?

Skeletons are good only in large numbers (necromancy), so try to preserve them from start lest they die.
Zombies are next to useless, save for being a meatshield or absorbing retaliations. However here Haste is your friend, preferrably with expert Air magic, so you buff other units too.
And about upgrading skeletons, I generally upgrade them when main hero has all the monster slots full. Then Necromancy will give you skeleton warriors instead of normal skeletons (though you will get less of them, IIRC).

Didn't know they would upgrade to upgraded skellies, for some reason.
But filling all your slots and hasting is something either not or often not available in the early game. Any ideas on how to get past what I'm thinking of as Necropolis's tough time clearing around its castle and playing the early game?

To start with you need to be very picky with what fights you start. You want to fight units you will crush with losing at max a few men and then start getting as much necromancy as possible to replace lost skeletons. Zombies are crap but they can take a beating so put them between your skeles and the enemy to act as a meat shield. Then with zombies and skeles take on other low end melee units to build your skele army. Stay away from shooters at the moment because they will wreak havok and just work your way around the beginning game building up your army.
Also forget wraiths they are just pure crap. Most the time I've got bonedragons before I even consider buying their dweling and using them. Its better to spend any money you would have spent on them getting vampire lords.
You will need to make risk assessments as well, if its the lumber and ore mine you will want to take those early on so more losses are acceptable. but for a spell shrine or a single resource you don't desperatly need yet just wait and take it later if its being guarded by enemys that will cause alot of damage.
Sorry for the incoherancy of the post its kind of remembered ramblings I have of the game.

If you play on lower difficulty, or have enough resources around, try rushing for either vampire lords or liches (or both).
Wights and wraiths regenerate, that helps too.
Also necromancy amplifier plus hero specialising on necromancy (they are two, IIRC) can quite nicely boost your skeleton numbers after a few fights. And don't forget first aid tent.

Definitely try to get Liches or Vampire Lords as soon as possible. Make appropriate use of magic, and don't try to purchase every troop type. Get your gold income up initially but try to have at least 4 creature dwellings by the end of the first week.

With this town I tend to play a little more cautiously at the beginning of the game. If the stacks are too hard I'll wait till the next week and reinforce my army. If you can get it so you overwhelm the enemy and lose few troops you get those back and hopefully more with necromancy. You'll want a decent magic casting hero over a combat one as well, being able to haste your skeletons or cast a good lighting bolt on a unit about to attack helps alot.
I personally think wraiths are a waste of gold. They die to easy and don't really hit that hard either. Dreadknights might be a bit high to go for first but vampire lords are amazing. They are one of your best units. It has to be the upgraded vampire lord though and not the normal vampire for their life leech ability. They recieve life and replenish their dead with the damage they deal against living enemys. So once you start getting their numbers up they are very hard to kill, most the time you won't lose any in a fight.
Its probably one of the most powerful towns once you get them going. They take a bit of practice to get used to how to play them early on but necromancy is such a powerful ability in the game that you start walking over your enemys with hordes of skeletons.

Just started the Necro campaign and my first impression is... i need more ranged units. :|

Are the Liches really the only thing Necro Cities have in that regard? Skeltons and zombies take forever to reach the enemy and getting enough of the other units takes way too much time.

Unfortunately Liches are it for necro ranged units in HOMM3. Try to aim for vampire lords as quickly as possible (their ability to resurrect when attacking will keep their numbers from dwindling unless you let them really take a beating), and just try to avoid fighting any ranged stacks until you've built up a decent army of higher tier creatures.

Necro had the same weaknesses in HOMM2 as well. Their flyers are meant to make up for the relative lack of ranged units. Ghost Dragons and their aging special can be quite nasty (halves the HP of the target stack).

The thing is Necropolis is weird. In most of the other towns, the 7th level unit is the main unit and the rest is there to support it, in the necropolis, the main units are vampire lords and skeletons warriors. Dread Knight, Liches and Ghost Dragons acts as support units. Zombies and Wight are useless, don't build or hire them except when you have too much money and nothing to do with it and put them in the skeleton generator.

My building order with Necropolis:
On the first week I concentrate on getting the Vampire Dwelling, Castle, Necromancy Amplifier and upgraded Vampire dwelling. On the second week I only hire the Vampire Lords and concentrate on City Hall, Liches and Dead Knight dwellings. Skeleton Generator and the building to get extra skeletons are build somewhere during the first two weeks. Capitol, Bone Dragons and upgraded creature dwellings I build after the second week.

My tactics so far:
Animate Dead with Expert Earth Magic trumps Death Wave every time.

A hero with nothing but 16 to 18 Vampire Lords can kill most wandering monsters without a single loss, let them do most of the job to minimize other units loss.

Always defend your skeletons. Don't be afraid to hire mule heroes for your Vampire Lords heroes to trade the skeletons in between two fights to prevent your skeletons from suffering too much loss in tough battles or when you attack ranged monsters. It also prevent them from slowing down Vampire Lords heroes. You can also use these mules to carry non-undead monsters who join your army so they can be put in the Skeleton Generator.

I agree wholeheartedly with blueskirt4. The Necropolis is my favorite town hands down. The key is going straight for the Vampire Lords (blah!). Once you get about five VLs and have a good number of skeleton warriors, you can chance the battles and come out relatively unscathed.

A trick I would use to always raise skel. warriors after battles, even when I just had SWs and VLs is to fill my other slots with 1 SW each, that way I don't get regular skeletons--of course, this only works as long as those single SWs don't get killed, but that's usually not a big problem. And once the SWs start piling up, I just had a whole bunch of large SW crews wandering around the battlefield.

As for the other units, zombies, wraiths, dreadknights, and bonedragons end up sticking around in the towns for defense or walking around with my second string hero. Once I've ot enough power liches amassed, I throw them in with my main hero and his/her SWs and VLs. And as others have said, zombies are very good fodder--they're a bit tough to kill, so just walk them into the middle of the action, which granted takes a while, and let them eat brains.

But I can't say it strongly enough: vampires, vampires, vampires! Well, vampire lords anyway. Once you get enough of them, prepare to stomp all comers. With expert earth magic, expert wisdom, animate dead, & town portal, you're good to go.

What, people actually use Something/Something/Expert [Blank] Magic? So far i found that to be a waste of Skill Space. \:|

Absolutely!

Read the advanced and expert effects of those spells and you'll see: Spells cost less, are more effective, heal or deal more damage, affect more or all units.... In the case of Town Portal you can choose which town to go back to. Teaching all elementary magic skills to all your heroes is a total waste of course, but not teaching them one or two elementary magic skill in addition to Wisdom is a big mistake. It's just a matter of choosing the element that will be the most effective with your army and your town library (since each towns have different probability of acquiring specific spells).

If I recall correctly, Necropolis libraries almost always have Animate Dead, Death Wave and have more chances to get Dimension Door at level 5. Teach Air, Earth and Wisdom to your heroes and you'll have little armies that teleport all over the place and defeat most enemies without suffering loss, and Haste affecting all your units will solve your problem with Necropolis not having enough ranged units.