1. Pinpoint the time of day you are most "adequate". For instance, I know that I shine in the afternoons, therefore I study NEW! material in the afternoons. That's, of course, not to say I can't study in the morning or at nights.
2. Make sure you are well-rested, that means get a good amount of exercise and sleep like a baby at nights.
3. Make sure your diet is balanced. That said, get intimate with your personal health, if you haven't by now.
I advise taking all "brain power" food recommendations you find by googling with a large spoon full of a salt. The common theme is people are looking for some clear cut definitive ways to "get better". Well, it takes a lot of trial and error and there is, sadly, no cookie cutter way of achieving it. The three things I suggested are by no means final.