A check raise is a move that every aspiring poker player should have in their trick bag. Basically it means that you check to your opponent, with the intention of raising his c-bet. This means, that you can only perform the check raise in poker, when you are out of position. A check raise is often shortened to XR, and being out of position, is often shortened to OOP. 

As an example let's say that you open from UTG and you get called from the CO, and everybody else folds. The flop comes, and for whatever reason, you decide to check (X) to the CO. The CO c-bets, and instead of folding or calling his c-bet, you raise it. You have now successfully executed a check raise. 

 Normally the check raise size is 3 - 3.5 times the c-bet we are raising. But - assuming we are talking a no limit version like the hugely popular Texas Holdem No Limit, there are, as the name of the game implies, no limit to how much you can raise. 

If you have the nuts, and you expect that villain will call your shove - go ahead and shove. If you think he will call a 4x or a 5x raise (that is 4 times or 5 times the c-bet), you can do that. Whatever size, you estimate to be give the highest Expected Value, is the correct size. 

 There are a few reasons why a thinking player would consider opting for a check raise rather than a standard c-bet. If you are playing against alert opponents, and you only c-bet when you have the goods, they will quickly notice, that they can just c-bet whenever you check to them - because you are basically telling them, that since you are not c-betting, you have nothing. 

So by showing your opponents, that they can not automatically c-bet profitably against you, whenever you check as the preflop aggressor, you make it harder for them to play correctly against you. 

This reason is even sweeter, when the preflop caller has proven to be very aggressive, betting and stabbing left and right, whenever someone showed the least sign of weakness. 

Another reason could be that you have flopped a very strong hand, and the board texture is such that it seems hard for your opponent to have hit anything. This can, under the correct circumstances, be a good reason to try a check raise, if you are certain, that villain will fold to a standard c-bet. Be very careful though, so you do not start slow playing all your premiums. You should choose the right spot, and the right opponent, before you consider check raising. If you have seen a passive villain checking back value hands several times, you should not try check raising. 

 Sometimes you hear coaches suggesting that you should occasionally check raise your strong draws. The reasoning is that you actually would not mind if the flop was checked through, so you sometimes get to see the turn card for free, while your hand is strong enough for you to also wish to start building the pot, in case you hit your jackpot. 

Naturally you should incorporate all these reasons into your check raising arsenal, when you start check raising, so your opponents will not know for sure that you always check raise with the nuts, and never with a draw - if you let them get this read on you, you are making it much easier for them to play correctly against you - which is the very last thing you want.

As with everything in life - as well as in poker. Having learned about check raising does not mean that you should check raise every single hand.

Or as Jonathan Little puts it in his book "Secrets of Professional Tournament Poker" (which we will complete the review of before too long): Be sure not to overuse this play. It will become a costly leak if players figure you out.

Go through some of your hand histories, where you are OOP and you think that one of the reasons above is in play. Then for each hand closely consider villains range to determine if a check raise or a c-bet would give you the highest possible EV for the hand.