As the others have said, stay away from any sort of bright lights or screens, it messes with your brains hormones to keep you sleepy. Also, WBTB is a technique to be used as others, to augment them and complement them, not just to be used alone. A good way to do WBTB is to try and train yourself to do it naturally. After every dream you have, you wake up briefly but most people don't remember it. You can, using mantras, get yourself to properly wake up after every dream. This can help with recall as well. All I tend to do for a WBTB is write down my dreams I've woken up from, and then read through a couple of my older ones, so that I keep my mind focused on the topic of dreaming, then head back to sleep.