I can give you some general tips:
(1) Summas are always best when dealing with competitive programs. It seems obvious, but keep your grades up.
(2) Your LoR need to be top-notch, coming from professors who know you well and are willing to put their professional reputation on the line. That being said, try to make sure your recommenders have some sort of reputation in their field. The more well-known they are, the better.
(3) Try to show some initiative outside of school, pursuing your interests without being forced to.
(4) Before you start dealing with your target school's faculty, read some of their major works
(5) Fit is really important; apply where you will be at home.