The continuation bet is a valuable weapon in a poker players arsenal, if it is used properly. When you have raised preflop, and you then bet after the flop, whether you hit the flop or not, that is a continuation bet or C- bet. Basically you are telling your opponent that you had a good starting hand before the flop and after the flop that your hand is still good if not better. As you are the aggressive player in the hand you are going to have the initiative in the hand and your opponent should fold.
Most players, if they do not already have a made hand, will miss the flop completely, so a show of aggression will push weak hands out of the pot. It is unwise to make a continuation bet every time that you raise pref lop, because you will be seen as predictable by your opponents and you could end up being trapped by a check raise.
There are different types of flop that will make for a C-bet if you hace raised preflop, if a high card like a Ace or a King comes on the flop, a continuation bet will give your opponents the impression that you have improved your hand, whether you actually have or not. Basically, if you missed the flop when a high card comes you can make a C-bet to represent the pot. Another good flop that may call for a c-bet is a lower flop that probably will not have helped your opponents hand. A flop like 2c-6h-Td may not have helped an opponent but a well timed C-bet will force a player holding cards like Ac-7d to fold.
When will a C-bet not be so succsessful?. Playing at lower limits it may be harder to force opponents to fold, as less experienced players will be willing to call with any two cards. Remember better players will be wary of the times that you make a C-bet. If you do it too often, players may come over the top of you and if you have missed the flop that is not the situation that you want to be in. If the flop may help an opponent to draw to a flush or straight, then it may be wiser to check instead of bet.
The size of your continuation bet is also important. The standard is usually about two-thirds of the pot, you should always bet the same amount whether you hit the flop or not. With practise, making the correct C-bet decisions will get easier as you will be able to read players more effectively