Playing poker online is no different than playing offline in one sense.  You still have to think and reason.  It can be tempting to get a bit excited and forget some of your poker knowledge, especially when you're new to playing online.  You won't win with that attitude, though.

Also, you should think in the sense of always waiting until your turn to act.  There are check/fold and other buttons that you can push early.  That will cause the computer to automatically act for you on your turn.  It's not a good idea to play online poker without thinking, though.  It can cause your opponents to figure out that your hands are weak or that you aren't paying attention.

Watch Your Bankroll

This can be difficult, when playing online.  Due to the speed of online games and the fact that you can play multiple games at a time, you're likely to win or lose a lot more per hour than you're used to in live settings.  This means that you could get caught up in the games and lose track of your earnings or losses.

One of the best ways to watch your bankroll is to simply pick an amount to deposit and not go over it.  Some online poker game sites even allow you to set deposit limits.  That way, you can avoid the temptation to spend more than you reasonably should or can afford.  This is especially useful if you're worried about developing an addiction to online poker.

Use the Website

You should also use the poker website that you choose to your advantage.  After all, many poker websites have statistics, tutorials and tips that are designed to help you out.  Some even offer quick notes that you can take about certain players or about your play, in general.  All of those things can help you if you use them and hurt you if you don't and others do.