I think what kooky mentioned is especially helpful. The reality check needs to be used as your back up to your question of whether you are in reality or not. Whenever you encounter strange situations or dream signs you should do an RC. Its great thing to get into the habit of doing.

Remember that this shouldn't be done automatically and just passing it off, it needs to be done where you question your reality. Some people just reality check without thinking about it and when they have a dream they just pass it off in their dreams.