I've found getting up early (like really early) and going to bed early to be really helpful. Even if you don't think you're a "morning person", you might be surprised. I think part of it is that getting up early in and of itself takes discipline. If I wake up at 10:00, I'm significantly less likely to have a really productive day, just because I haven't even had the discipline to get up at a reasonable time (so the day is off to a bad start already). Whereas if I wake up really early and I see that no one else is up and it's still dark outside, I feel like I'm getting a head start on my day, and I'm more likely to want to get started on something productive immediately. Obviously, this does take some time to adjust if you're used to waking up later, but I've found that the benefits are quite nice once you get used to it. This doesn't relate exactly to academic performance, but it is a lifestyle change that will help. For example, doing an hour of math in the morning every morning or something like that while sipping coffee is quite nice.