Laptop designers have grown adept at hiding or masking the power button. The most recent trend is to put the power button under the laptop's lid; you must open up the laptop to find and press the power button, turning the laptop on.
Older laptops may have the power button anywhere, usually along one of the laptop's sides: front, left, right, or back.
The power button may be a spring-slide switch that you must push in one direction and then release.
Some power buttons are tiny push buttons. There’s no click or bump to the button's feel; you just press it in with your finger and pray that the laptop obeys you.
If the power button is easy to overlook, you can put a red sticker dot by or near its location. Even so, you should find that a few times after opening the case and turning the system on, you’ll remember where the button is. Of course, this doesn't help you use anyone else's laptop, because the power button is never in the same location twice.