I do these throughout the day at random intervals. As often as I remember but not as often as 5 minutes or whatever. Usually 30-2 hour intervals.
If it's in stars, that's what I do. If it isn't, that's what I think.
"Am I dreaming? If I am dreaming then I will be able to breathe with my nose pinched."
*Pinches nose and tries breathing*
"Am I dreaming? If I am dreaming then my hand will look different."
*Looks at hand and counts fingers individually.*
"Five fingers."
"Am I dreaming? If I am dreaming then my finger will go through my hand."
*Imagines the feeling of index finger going through opposite hand and tries it*
"Am I dreaming? If I am dreaming then how did I get here?"
*Thinks of the path he took and retraces it.* It's usually "I am at the computer so I have been here for several hours though.
*Thinks of the results of the various reality checks.*
"I am awake."