SAT Preparation (Better Score Second Time)

New SAT came out about a year ago. I want to take the August SAT (if there are any seats left since at this point, it’s pretty full) and from now to then, I have approximately two months to prepare. If I must, I will take it in October. If I want to get a high score (1520+), please give me tips on how and what to self-study over this summer. Also, do superscores still exist?