While I'm sure higher limits demand more attention, at the lower limits I play at for now, no one is really trying to mix it up. I use PAHUD for the stats on aggression, playable cards (VP$IP is IMO the most important stat to use because it indicates range preflop), etc. Obviously I miss if they'll chase draws w/o
odds, but then again about 99% of the players at those levels do. I just recently moved up from 4 to 6 tables at once and found out I can handle it pretty easily. Now although my per-table profit may be more when single tabling, I don't think I could make a higher overall profit (ie 6 times per table profit) just single tabling. Oh and I listen to music, helps either get me ready to play or calm me down. I think it helps.
Bad habit? Chasing losses. I think I've gotten past that, haven't done it in the past few months, but I used to do that every time and although once in a while I'd make it back, I'd always end up busting.