Read through the chapters in your textbook before you cover them in your advanced placement classes. Doing so will help you to understand the lectures in class when the time comes to cover those chapters.
Develop your analytical and problem solving skills. Many college courses such as philosophy and ethics classes have multiple solutions to a problem. Developing your analytical and problem solving skills while taking advanced placement classes in high school prepares you for these types of situations.
Work on your writing skills, which are important in college where you will be expected to be familiar with all styles and formats of writing. You also will be expected to know how to properly source your papers according to APA, Chicago Manual and MLA formats.
Develop great study skills. Do this by making a study schedule and sticking to it. The study skills you develop in high school will help you immensely in college.