Implied odds is basically the ratio between what you expect to win when you do hit your hand against the amount it will take to stay in the hand. Preflop, small pocket pairs are a good example of a hand that has huge implied odds.

If you do hit your set, you will probably make a lot of money against an opponent with two pair or top pair and top kicker. Suited connectors also often have good implied odds, especially if you raise on the button with hands like QJs and JTs every once in a while.

People will usually be surprised if you hit your straight or flush against their two pair or set. Slowplaying large pocket pairs (AA-QQ), although it can often backfire, gives you a well-disguised hand and good implied odds (assuming your opponent doesn't outdraw you).

If your opponents have a good read on you, your implied odds drop significantly. If you always check/call down to the river with a small flush draw or straight draw and your opponents know this, you can't really expect to win more bets from your opponents when you hit your flush or straight.

Remember to keep implied odds into the equation when you are debating a call and you will be a more successful player!