Whether you are having a panic attack and need a little extra air or you just want to see how powerful your suggestion of yawning is on those around you, try to make yourself yawn. You can get more air into your lungs, or you can force everyone within a mile radius to yawn along with you.
Think of yawning and picture yourself yawning in your mind. Sometimes the thought of a yawn is all it takes to make yourself do it.
Watch a video of other people yawning. Yawning is very contagious and a video of a yawner can make you yawn.
Make yourself yawn by physically opening up the back of your throat. You know where the spot is and once you have opened that portion of your throat and thrown your jaw open wide, you can make yourself yawn.
Read a book--it helps if it is not incredibly interesting. The tired feeling behind the eyes can make one feel tired all over. Read for a bit, especially if you are trying to become tired, and it can help you make yourself yawn and be ready for bed.
Stretch to help make yourself yawn. Even if it is in the middle of the day, reach your arms up and back and do the morning stretch to bring on the yawn.
Open your mouth wide, unhinge your jaw and gulp in air. This can easily trigger a yawn, even when you aren't tired.