If you are a beginner at Texas Holdem poker, here are a few elements for correct play. If you are experienced already, you can still read this as a refresher.
The most important thing that all PokerStars pros know is to raise and reraise big pairs and big aces at the first round of betting, in other words pre flop. The main reason for doing that is to make the pot size larger when you have a high chance of winning it. The second reason is that you want weak hands to fold, because there is hardly a worse situation than getting your rockets cracked by a garbage hand like 96o when the flop comes K96.
Another key point that Phil Hellmuth mentions in his book is to avoid drawing to the idiot side of a straight, i.e the lower side of the straight. If you hold 98s and the flop comes JT4 rainbow, it is not too good an idea to bet or call big bets with such a straight draw. Because you will often win a small pot or lose a big pot. The reason is if the pot gets big someone else has a big hand and if a queen comes, there is a good chance another player has a higher straight than you.
The next tip is to fold unconnected cards of medium strength most of the time. Even low pairs should be mucked unless you are set mining. But even if you hit a set, there is always the chance that another player has a higher set, and it is very costly to lose a huge pot in a battle of sets when you are dominated like that without mercy. Remember you want to win big pots and lose small pots, so the habit of folding such low cards is a good one to have.
Finally top poker pros say that learning how to catch a bluff is a fundamental skill to have. Learn to understand which of your opponents bluff a lot to attempt to make you fold your good hands. Try to be not predictable yourself. Master how to bluff perfectly, since this will potentially add a lot of money to your wallet. Study your competitors to see if they are easy to bluff, or if they bluff all the time.
Even if you spend a lot of time playing online poker, you may not win money immediately. You do need to first sharpen your skills to become good at the game of poker so read articles like this one to learn strategy.