The goal, using reality checks, is to:

Do reality checks often, and consistently, when you're actually _awake_ , to the point where it becomes a habit.
This somehow transfers via your subconscious and it finally happens in a dream.
It doesn't really help to say "Ok, the next time I think I'm dreaming in a dream, I can do this RC"
You don't "choose" to do the RC when you're dreaming. You just happen to have a dream about doing a RC. Because you do them all the time in your waking life. It's the shock of the RC failing that snaps you into lucidity.