Poker is a game of chance but also one of pure competitive skill. Like any other game of chance that involves a significant amount of luck, the best players will always win in the long run. Poker requires a significant amount of raw technical skill to learn optimal frequencies & hand ranges to maximize your edge in the game.
You need to learn how to read your opponents and understand their tells (eye movements, idiosyncratic betting habits etc.). This will help you figure out when your opponent is bluffing and when they are simply calling for the pot value.
Another important part of the game is learning how to manage your chip stack in each hand. A good strategy is to raise on a strong hand when your opponent raises and fold with weak ones. This will give you a positive expected value.
There are also certain times when you should simply call a bet. This is typically when you have a hand that can pay off if paired. This is an effective way to keep your opponent from making ludicrous draws and make him chase the pot.
It is also a good idea to play more hands in late position. This will allow you to see more cards on the flop and make better decisions. It will also enable you to control the size of the pot since you will have the final say as to how much to bet.