The most important thing I find in ring games is to select the right table.
I usually will watch a table or several before sitting down.
Look for a table where everyone is looking to limp in. If you open for a raise (assuming you have a hand to do it with) usually half of the limpers will go away. The ones that stay around will either be calling stations or probably have you beat.
In the smaller limits, you find a lot of fish betting their Ace rags or K7 or some other marginal hands just to see a flop.
Be careful of the calling stations, they will stay in with middle or lower pairs so bluffing them isn't always effective.
Make notes on the players, if they overplay an AK, AQ even though flop is all small cards, do they bluff Ace high, or are they always looking for that straight or flush to hit on the river. These players can double your bankroll if played correctly.
Finally, and I know some people will object, but checking the nuts, acting like you are the one fishing is (IMO) perfectly acceptable if you want to win a good sized pot.
Go to Full Tilt Academy and watch the lesson on online tells
, it is very good.