You don't need to know too much Math. But what's beautiful about math is that it develops your thinking a lot and knowing how to solve Math problems will help you solve real problems in a programming language of choice. So what you really need is to develop your logic by solving a lot of problems both in the field of Mathematics and a certain programming language. Here are a few : http://projecteuler.net/problems

You should know precalculus.

http://en.wikipedia.org/wiki/Precalculus

Math and computer science go well together so knowing solid math fundamentals will help. Also a basic understanding of programming and how computers work won't hurt. More importantly (and this applies to everyone getting ready for college) you should know how to learn. Being able to learn new things will take you further than nearly anything else.