The strength of your hand determines how you bet in a Poker game.

Great starting hand
Be patient and lay low in the beginning. Don't start out betting too high, try to draw people in and keep as many players in as possible. Don't raise too high (perhaps a little below normal). Call but do not raise in response to another player's raise. In middle rounds, make normal bets. In the final round, make your big bets.
Average starting hand, with vulnerability
Exaggerate the strength of your hand by betting as much as possible to reduce the number of players that stay in. At any point in late betting intervals, if you find that you don't think you can win, fold.
Hand that can improve with the draw
This hand is currently weak but has great potential to improve as cards are drawn (such as a four card straight or flush). Try to stay in while betting as little as possible. Get out when your odds of getting the card you need don't look good.

Long shot hand
This hand has a small chance of improvement, but may show some promise, such as three cards towards a flush or four cards towards a straight. Try to stay in while betting as little as possible. Get out when your odds of getting the card you need don't look good.
Bad starting hand
Fold as soon as you are required to call a bet.