I'm new. Yes, new. Please enlighten me.

[Wyrm]

Yours truly managed to f*** up a paladin and a sorceress (yes, 2 chars one after the other) as a startup to the game.

That's nothing. It took me about 10 tries before I finally got a nm-viable character, and a few more to get into hell. I didn't really mind starting over, so it wasn't that big of a problem.

The best advice I can give on picking a char is to look through the builds that have been documented both here and at the Basin to get a general idea of what works and appeals to you. Then, just make your own alterations/tweaks to the build to suit you. Generally speaking though, until a build hits level 35, it won't have enough skill points to give you an idea of what to expect for the rest of the game.

A Necromancer is going to have the hardest fight against Diablo on normal, simply due to the fact that he's not going to have any real damage from his skills at that point. Everyone else has at least one skill that will eat through bosses by that point.

3. Maxing Resistances for Fire and Lightning is handy, although Diablo's breath weapon also has a physical component.

That sounds like a very Breath of Fire thing to say. Or maybe I'm just too much of a BoF person...