Continuation bet can be a very powerful poker tool for winning money, but if used excessively c-bet can become your downfall.
There are several truths about poker. First of them is that people miss their flops most of the time. And if you raised pre-flop and you opponent missed, then by using a continuation bet you just pick up the pot regardless of what you are holding.
That is usually the desired scenario. You bet, he folds, we move on to the next hand. Sometimes your opponent will call and you will be facing a decision on turn - bet or check.
I have seen people who make continuity bets every time they have raised pre-flop and it seems to be working for them, especially now. If you have noticed, poker players have become less aggressive, more passive. I think it's because everyone values money more in the face of financial crisis.
One more truth of poker - to win, you have to know your opponent and play accordingly. So if he's passive, you have to play more aggressively than usual. If he's aggressive, try catching flops and take his money. If he's loose, get your cards and make him to call anything. Sounds easy?
The same truth goes for continuation bets. The more you know about your opponent, the easier it is to know whether you should use a c-bet or not. If he's passive, I would suggest using continuation bets all the time, because he will fold most of the times. If he calls or raises, you know that usually he has you beat and just fold. In the long term you win.
If he is aggressive or loose, continuation bets could backfire, because usually these players will call or raise and you will have to fold if you have nothing in hand.
One more thing to know about continuation bet - the more you use it, the more opponents will notice that. And if they notice that, then you are doomed to get raised more often and called more often and bluffed out of pots.
Be diverse. Use a continuation bet in about 20% of pots and you should be fine. Think about it. If you missed your flop and checked, maybe turn card will be better for you.