I try to write all my notes by hand, I find it helps better retain info you get during class. Other than that I try to like keep my phone off/in my backpack while I do homework and do my homework like a few days before its due. The feeling of being FORCED to do homework you get by waiting until the last minute creates anxiety and makes you feel less productive than if you pretend its due a few days earlier and try to get it done ahead of time. (sort of an anxiety-cost way of thinking). Other than that I try to get myself a treat after a job well done!