An RC is something you need to get into the habit of when you are not dreaming. Once you have made it a habit then when you are actually dreaming, it will seem unusual to get an out of the ordinary response from your reality check.
For instance, lets say your reality check is to have something written on your hand. If this word or sentence is always there when you look at your hand then it will become as natural as anything else you do. So when you are dreaming and you look down at your hand at some point the writing will most always be different, which should give you the realization in your dream.
Take into consideration that this does not happen quick at all, patience is a virtue; especially if you rely on reality checks.