Reality checks are useful for a number of reasons. They help train your mind to questions reality and they also help you focus your intent of having a lucid dream.
Everyone for the remainder of this course, choose a reality check or two and decide how often you will perform it. Really put an effort into the reality check.
Don't just perform it and go on your way. Really question reality and imagine how your surroundings might be different if it had been a dream. Reflect on your surroundings, can you remember the timeline from when you awoke this morning? Can you remember what you had at your last meal? You all get the picture

Each night before bed if possible, make an entry in your workbook containing which reality check you performed, when you performed it, and how many times you performed it. For example:
Reality check: Try to levitate
When: Every time I passed though a door
How many times: 10