For reality checks to work, you need to think of them in a dream. You can either wait for yourself to randomly think of one.... or force one to happen. Easiest way to do that is to link the idea of doing R.C.s with lots of things, mainly your dreamsigns. I assume you know what these are, but basically they are the most common subjects/objects/people/things that pop up in your dreams. If you can establish a mental link between R.C.s and those dreamsigns, you will think of R.C.s when you see a dreamsign.

Best way to build this up is to first find out what they are. For me, I play games a lot, so a lot of characters and aspects of games get into my dreams. So what I do is reality check or keep reality checks on my mind while I play my games. This is establish a link, much like how when you smell flowers, you think of your favorite flower or gardens, etc. You are so used to linking one thing with another, that they pop into your head because of the stimulant.

Basically, with enough linking, next time you see a dreamsign in your dream, we hope that this makes R.C.s pop into your head and you do one.