how to play aggressively... a little unsure

So,

I mostly play .25/50 $20 NL home games, but for the most part have been a break-even player.

My preflop hand selection is pretty tight, and I try to loosen up in late positions.

My question is this... where does the aggression part really come in?

I find myself in a lot of situations where I'm either:
(a) out of position with 2-4 people to act after me
(b) in late position, but there's already been a bet and 1-2 callers

How can you act aggressively in these situations? It seems like with so many players in the hands, you're not getting much fold equity by playing aggressively.

For reference, I'm typically raising about 4x the BB preflop to $2.00. Should I go even more? The stack size is so small relative to the blinds, that with a few callers, I'd be almost committed to any hand.

Thoughts?

[amoeba]

there are 2 purposes to aggression. to get value and to have better hands fold.

if the second option is not possible, then you have to be aggressive with a more selective hand range.