Here are some things that seem obvious now, but might not have back then.
1. Remember these three words, "It's a game." It is not important that you have the ultimate combo/killer character, if you are having fun playing you're way, then keep doing that.
2. If a deal seems to good to be true, it usually is. If a deal seems like it's not worth it, it usually isn't. If you don't know what something is worth and you are using it, keep it. You may miss out on a good deal once or twice, but this rule will save you ten times over.
3. Don't beg, pester or abuse. There are veteran players who treat this game like a religion who can make your playing experience abismal and the best way to get this sort of attention is to piss them off.
4. Plan ahead. 110 skill points, 505 stat points. At the very least, have a vague idea of where you want to put them.
5. Read. There is a virtual encyclopedia of information out there, if you have a question and it seems like the answer should be out there somewhere, it usually is.
6. Ask questions. Avoiding no.3, pester. And after no.4, read, don't be afraid to ask if you don't know. Better to find out now than spend two weeks compounding a mistake until it resembles insane intention.
7. My undead army kicks yours, live with it.
8. My Hammerdin kicks your undead army too.
9. Don't let people pick on your undead army, skeletons have feelings too.
10. I highly recommend... a) playing through single player at least once before Bnet. b) playing all the different characters through a couple of acts before taking one to lvl99.
There you go.
---------------------- RSPCS is watching you.