calling preflop raises in low limit NL

[kingofswing]

I find myself with a VPIP of about 15 and preflop raise of about 3. I think the VPIP is pretty good for my style, which is certainly a little on the tight side. My question is basically two parted. In full ring games, if there are two callers say, should I be raising with somewhat marginal hands like AQo, AJo, ATs, Axs, KQs, KJs, TT, 99? What about if I am first in? I usually just take a flop and see what happens, but I was wondering...

And just to make this post agree with the title, my other question is what about hands like that when it is raised to 4xBB in EP or MP by someone with a VPIP 40% and PFR 10%, do I call these and see what develops, try to beat him preflop? Do I ever play back?