How to get in the habit of brushing 2 times a day?

Alright.. So, for some reason I never really brush twice a day. I know it's gross, but until a few years ago I didn't know I was supposed to. Since I'm in middle school, I want to try and make a habit of brushing twice a day. Problem is, I'm lazy and forgetful. I'll probably remember then slack on it because I don't want to get up, or not remember then scold myself later. I want to do this also because I want my teeth to be whiter. They aren't the brightest right now. Any tips? Thanks!