Hey everyone,
Played Heroes II for years and loved it...but I must have been doing something wrong because I've never gotten good enough to get all the way through the campaigns. Decided to buy Heroes III this week, have never played it before. This game is awesome, but I've noticed that its even harder than Heroes II. What am I missing here? I keep coming back to these games in part because they're actually challenging, but I'd like to figure out how to beat the campaigns one of these days. Can somebody point me in the right direction?

In Heroes 2, it was often possible to pick up a couple of good cities, fortify yourself, build a killer army, then go on a rampage. In this respect, Heroes III is a lot less forgiving.
If fortifying was a strategy for you in the last game, try practicing a few maps on Heroes III as aggressively as possible. In the early game, be prepared to lose several of your troops in order to get to the next artifact/gold stash/town.
If you normally play on high difficulties, don't be embarrassed to turn the difficulty down a notch in order to play through a map. There's a bit of a spoiler about the different difficulty settings here.

Does difficulty level also affect your starting resources like in HoMM2?
Drat. I hate when this happen. As a player, I want the AI to be as smart as it can be, but I still want the fight to be fair (IE all players should start with the same amount of resources, about the same strength, AI should not be a cheating bastard and I should not be the only player they attack). If someone made a chess video game where when you increase the AI difficulty, you also start with less chess pieces, people would complain, they wanna see how good they are against the AI in a fair fight. Same for me.

Yes, it does, as in every other Heroes game.
On the lowest difficulty you have most resources and the AI has none. On the highest it is the other way around.
On hard difficulty you start with the samount of resources like AI and it plays best as it can. You can actually right-click on the difficulty buttons while selecting a map, so you will see a tooltip about what you can expect (I am speaking about Heroes 3 now).

In HoMM1, you could change the difficulty from easy to impossible, and you could tweak the AIs so they were either dumb, average, expert or genius, so it was possible to play with genius AIs on normal difficulty, or dumb AIs on impossible difficulty. They should have kept this option in other HoMM games if you ask me.

Agreed. Even though "Hard" is indeed there to give you an expert AI and balanced resources, it would be neat to be able to pick AI strength and amount of resources separately in every HoMM game.