Vanderbilt University has a decent “Preparing for College” section on its website. I like that it’s not “What does Vanderbilt look for?" They broaden the discussion and make it clear that this section is intended to “position you to increase your chances of success in college.”
Some of the advice:
"If your high school offers any advanced, honors, Advanced Placement, or International Baccalaureate courses, it’s recommended you pursue those as appropriate. You should challenge yourself without getting in over your head"
"As impressive as it may seem that a student is involved in numerous different organizations, it's equally (if not more) impressive to see a student who is involved in just a few organizations during high school and is in a leadership position in each of them. Think quality not quantity in terms of activities."
"Ask teachers from your core courses (English, Math, Social Science, Natural Science, Foreign Language) to write your letters of recommendation. Ask teachers who know you well or in whose classes you regularly contributed. Sometimes the teacher from the very difficult advanced-level course, where you worked very hard for a "B," may prove to be your best advocate."
"In today's competitive college admission atmosphere, even the most talented students need options. Your list should include safety, target, and reach schools that you would be excited to attend. There are thousands of accredited four-year colleges and universities in the U.S., so with careful preparation and thoughtful consideration, you will land on a campus that is right for you."