After decades of LD's I have settled into just one type of reality check... this would be a gravity check. Anytime I get this 'am I dreaming' thought in a dream I just jump. This has never(as far as I recall) failed to bring about lucidity as dream gravity, as we all know, is more like lunar gravity. However, I should further state that RC's are just one way of many that I use to become lucid.