As with any card game, poker is a game of chance. However, to win consistently, players must have other players willing to pay them. Thus, although luck plays a role in the game, winning large amounts of money requires good decisions based on probability, psychology and game theory.
The best way to become a great poker player is to play the game and observe how others do it. Observe not only the physical tells of your opponents (eg scratching the nose, playing with their chips etc), but also their betting behavior. For example, a player who calls frequently but then suddenly raises the pot is often holding a strong hand.
Another thing you should do is to learn the basics of poker hands and positions. Knowing what a flush is, for example, will allow you to determine if your opponent has one. This will then help you make the right decision about whether or not to raise, call or fold.
A strong hand is made up of three matching cards of 1 rank or two matching cards of another rank plus one unmatched card. A straight is 5 cards of consecutive rank in the same suit. A full house is 3 matching cards of the same rank plus 2 matching cards of another rank.
Top players fast-play their strong hands to build the pot and to chase off others who might be holding a draw. This is why you hear commentators at the World Series of Poker gush over the fact that a legend has laid down a pair of Kings when they know in their gut that they’re beaten. This type of intelligent lay down will save you countless buy-ins in the long run.