Look at your hands, feet, legs, etc. Are they the usual shape? Do you have the right amount of digits? Is any part of your body disfigured?
Try to find a mirror. What does your reflection look like in the mirror?
Test your strength and abilities. Clearly, if you can fly or lift extremely heavy objects, you're not awake
Try jumping on the spot. Can you jump over the moon, or maintain a jump for an abnormally long period of time?
Look at the ground underneath your feet. Does it look normal or not?
Are you able to shift objects across a room or area without going near them?
and on. …