No reality check is fool proof, so along with doing what melanieb said, have a repertoire of at least 2 or 3 reality checks you use on a daily basis.

If you think a reality check will tell you you're in reality, it will tell you that. So every time you do your RC, even if you're 100% sure you're awake, fully expect the RC to fail (tell you you're dreaming).

Good luck ^^