Set an alarm, chime, or any kind of prompt, once an hour or so. Then look at your hands and ask yourself am I dreaming? Look around your environment and convince yourself you are awake. Pinch yourself and generally just confirm that you are in an awake state.

The theory behind reality checks is that this regular routine of checking your hands will seep into your subconscious mind whilst you sleep and as you are confirming you are awake you will realize in fact you are not. Also, it has been suggested that the subconscious mind has difficulty replicating your hands. Often times when looking at hands in dreams they appear as melting stubs. This of course is another indication that you are in fact asleep.