avoid using electronics, there is a high chance of you getting distracted. don't lie to yourself and say that you'll be off your phone in five minutes and stay for the whole hour. you're just cheating yourself, be motivated to study and don't think that you're studying for the sake of someone else, because you're not. you're doing it for yourself.

try to use your textbook or class notes as much as possible, unless if you need to use an electronic devices to get access to your class notes, avoid them. 

i heard that many college and uni students take notes on their laptops, so you would need it if you're doing that but make sure to focus on your work and only that.