Well, try to do reality checks every time you possibly can. What they do, is tell you if you are dreaming or not. Many things in the dream world appear different than they are in waking life, such as your hands. The more you reality check, the more chances you have of doing a reality check in your dreams.

If you would like to write something on your hands, go right ahead. I wrote an A on my hands for a while, and it would remind me to reality check once I saw the A. Although, you might get questions asked from your classmates, which could get overly annoying.