^^^^^^^what he said.
You should look at every thing you do at a poker table like this:
Why am I doing what I am doing?
If you dont have an answer, then that is a good place to start.
I will give a couple of examples.
Limping in early position with a very strong hand - AKs, AA-QQ - because you have a player to follow who constantly raises limpers, and you expect to be raised here most of the time. VOILA! A REASON for doing something. Not that I think limping is necessarily the best move, but just showing a plausible reason why limping would be one thing to consider in this situation.
Just try to have reasons for what you do. Sounds easy, and is often not.
Go
here to read some beginner strategy.
PS: limping is generally just to be avoided in micro stake nlhe online games. Punishing limpers is to be enjoyed.