Hey man, welcome!

Yeah the looting is a PITA. Best thing I've done is just configure for auto loot. If you're running multiple instances on one machine then get the TweakUI PowerToy from MS so you automatically focus on whatever window your mouse is over, that helped me a lot.

As far as Quest/Instance grinding, that's almost as debated as class selection on this forum. I will say thought that the 20-60 extra quest XP really adds a lot to the questing angle. Regardless you're best doing whatever you enjoy the most. I primarily quested from 1-60 but now in Outland my strat is to rest all week (what? no WoW?!?!) and then run instances all weekend with double XP goodness (1600/kill/toon in Ramps).

For Civilians? Grow a thick skin. Hide your alts in a lesser used building or under the stairs in IF near the bank (for some reason NO one ever sees my shaman under there). I try and say SOMETHING in /say just so that people know there's a real person attached. I also reply to whispers, but only so long as they'll stay civil. Most common comments?
1) joeplayer: Nice Bots, elo: Not bots, it's called multiboxing, look it up on wowwiki
2) joeplayer: You gonna sell those accounts, elo: Have you ever done the math on that? It works out to be less than minimum wage
3) joeplayer: Man, someone's got no life, elo: hey, do a /played and tell me what you got. So far (at 60) I've got less than 2 days each in these how about you?, elo: Well, what is it? <There is no player named 'joeplayer'> ROFL!

Either way man, don't do anything that violates ToS (and correct Multiboxing doesn't) and Blizz is on your side so the idiots just don't matter.

GLHF