usually people do a reality check after they noticed something is out of place and suspect it's a dream. Then a reality check is done to reaffirm you are in fact dreaming. So i woulden't call this technique a reality check. but in order to know u are dreaming something about it has to be different than normal. If you always have a D written on ur hand while u are awake. And do a reality check every time it is gone , like pinching ur nose and try to breathe trough it the absence of the letter D acted as a dream sign. I don't know why you don't become lucid either but maybe it is because you don't question ur situation often enough while u are awake.