Play fundamental ABC poker. If you are not sure what that means, check out the beginners digest and read everything.

Highlights of ABC play:
-Play most of your hands in position. (HJ, CO, BTN)
-Seldom call. Be the aggressor on almost every hand you play. Passive play is losing play
-Bet your strong hands the same as your bluffs (balance your range.)
-Do not call 3-bets. 4-bet your value range, or fold. For 6-max, value range is JJ+, AK. For 9-max, QQ+, AK+
-3-bet your value range minimum of 3x the original raise. 4x-5x is fine at <5NL or as a squeeze. (squeeze is 3-betting after a raise and a call(s) )
-C-bet 100% of flops heads up
-Barrel turns when your perceived range improves (a face overcard hits, a flush comes in, 4 to a straight hits board etc).. or if you have what you believe to be at least 5 outs.
-I would suggest no 3-barrel bluffs.. only bet the river with strong holdings, ie. top pair+
-Bet-fold, do not bet-call or check-call. At 2NL a reraise usually means strength.. lay down anything < two pair when reraised. There are exceptions, but for the most part.. this will get you on the right track.