Check/raising your opponent is one of the strongest betting signals that there is.
Whenever there is a check and then a raise made by a player, it means that the player wanted to not only build the pot as large as their bet could make it, but they also wanted you to bet first so that they could make the pot even bigger. This is a huge signal and you should always watch out for it.
Check-raising is also a great tool to have in your collection to help take money from bad players who don't realize what you are doing.
A check/raise on the flop is very uncommon except in 3bet pots. Normally that is the only time you will see the play happen on the flop. This is normally pocket A's vs another high pocket pair. The player with pocket A's will check so that their opponent thinks that they have AK and missed which will make them bet. Once the extra bet is in, the player then raises to get even more money into the pot that they are winning.
This is a very quick way to get your opponent to feel committed with a hand like QQ whenever they are clearly crushed.
Check-raising on the turn
A check/raise on the turn is a different story than on the flop.
Whenever a player check/raises you on the turn, you should more than likely fold. Check/raising on the turn is one of the strongest plays in hold'em and it normally means that your opponent has the nuts.
Unless your hand is extremely strong, you should avoid making calls on the turn when your opponent check/raises you. Against weak players you can use the check/raise all in move called "stack-a-donk" to get their entire stack.
You c-bet on the flop and then check to them on the turn. You have to know that your opponent has a made hand, so that they will surely bet on the turn and then you raise them all in. The player will normally feel like they are committed to the pot and make the call even though you know you have them crushed.
I am not a fan of check/raising on the river at all. The river is your last chance to get money into the pot. Whenever you check you are giving your opponent the chance to check as well and you earn no value at all. When you bet on the river you are giving yourself the chance to win more where checking you lose that opportunity.
That is why position is so important in poker. If you knew what your opponent was going to do, then you could play accordingly, but you don't when you are out of position.
A check-raise is a very powerful move in poker and knowing how to play against it and how to extort it is very important.
With all of the money you will save from avoiding getting check/raised and the money you will win from check/raising, you should learn as much about the play as possible. Make sure that you add this incredible maneuver to your arsenal.
If you want to learn more about check raising, ask Maria Ho, a gorgeous poker pro who plays often at PokerStars and Bodog Poker.