Something that may work for you, it does for me.

I found that when I play a full table, success comes from playing super tight aggressive. Other folks at a full table generally respect raises and continuation bets. So your aggression can pay off.

At a 6max table, I find that aggressive pre-flop (unless monster starter) is just spewing chips. I think the reason is, that everyone wants in community hands no matter what the raise is. So a 3 - 4 bet raise will still get 3 - 4 callers out of 6, and if you miss you basically lost your raise.

So my strategy at a 6max table is the following:

1. Passive preflop: i.e. dont raise mid-raising hands AQ,AJ,
2. Raise high suited connectors on button or 1 off, hoping to get a chance for a free card if needed after flop.
3. Get in as many pots as possible with marginal hands when community is involved. Especially if somone is raising 3 - 4 times blind.
4. 2 pair or better after flop, play hyper aggressive.
5. Got to be willing to put your stack in the middle with the edge. Too many people still calling with middle pair let alone a top pair hand.
6. If your table is raising every time 3 - 4 BB's or so, dont be afraid to limp with a monster, and push after it gets raised. Someone will still call you with something you dominate.
7. Had to add: If someone pushes all in in front of you representing an overbet. Dont call unless you have a set or better, or a good read on them. If you have a good read on them, I still think 2 pair or better.

These are just some of the things I do when I am building at the lower levels. I buy in short, therefore I can push the edges when I hit.