Well assuming you are a winning player (most often not the case), the first thing to learn is bankroll management then. You shouldn't play games that can easily crack the roll.
For example, if I were playing $5/$10 no-limit holdem I would want a $10,000 bankroll or I won't even consider playing. Be careful with the roll, and don't move up a level unless your roll supports it. If you keep at least 500 times the big blind of the level you play and are a winning player you are pretty safe but the first trick to playing poker for money is picking the right games and playing safely within your roll. Even if you are a winning player, if your roll isn't big enough bad luck can crack it, so you need to keep enough on hand to be able to handle the swings.