Where are the best places to level up?

[Liberator]

at or around lvl 20 in normal?
at or around lvl 40 in nightmare?
nevermind about Hell, I have yet to build a character that can live for long in hell at the level I get there in. It's obscene! I have a sorceress that is focused in cold, she has maxed out the orb and almost maxed cold mastery, but it seems like every single creature in hell is immune or all but immune to her spells. I gave her a magnificent sword so she has a backup, just in case, she does 300-1400 damage with it and she can't kill a single fuken zombie before she get walloped.

[Pitboss_2000]

Lvl 20-25 in Normal: Cow-runs. Just look for a game with the word' cow' in the title, preferrably with a lvl 70+ character in it to do all the actual killing. At lvl 24-25, kill the Ancients, then proceed with Baal-runs.

I'd do normal Baal runs until I hit lvl 45, then look for a boost through NM and immediately start doin Baal runs in NM once you reach the big fat guy. (I'm usually around lvl 47-48 when I get there)

[GenXCub]

Shouldn't it occur to you that if you can't kill monsters in hell, that you're doing something wrong? Why not get 2 types of attack? (the sword doesn't count unless you're an enchantress).

[Elgar]

it depends on how you play.

i generally dont have trouble leveling until i hit about 24 (somewhere in act 3 norm), but of course i do all the quests solo, and then i start leveling decent in Act 5. Im usually 35-36 by the time i hit NM, and i like doing NM countess/Andy if i feel i need a little more experience (im not a fan of normal Baal runs, its just not my thing)

If you are rushing, pitboss is correct that cows (if you can kil them) are the best til ~25 when you should switch over to normal baal runs until you hit 45.

However, if you cant kill cows, the flayer jungle is a decent place for lvl 20. There are plenty of monsters, and they have mlvl 21.