Most colleges and universities will require four years of English in high school, so make sure your high school at least offers, if not requires, four years of English. Some high schools will offer the option for honors courses, which are a more advanced form of college preparatory work. Honors courses are a way to better challenge yourself, as well as gain an idea as to how you would fare in a college-level course.
Colleges will generally require successful completion of three to four mathematics courses. Advanced Placement and honors courses are specially designed to prepare students for college by moving at a quicker pace and covering sometimes more advanced material. Colleges will usually look for completion of Algebra I & II, as well as either Geometry or Pre-Calculus.
There are numerous books that offer college preparatory work and help. Some books focus on a specific subject, such as science or math, while others offer preparatory work in a number of subjects. These prep books essentially complement other preparatory courses in reviewing and explaining concepts necessary for college.
Independent organizations such as Kaplan's offer outside help to both prepare for college, as well as prepare for standardized tests required by colleges for admission. Such courses generally focus on learning tools and strategies that help a student understand complex concepts and ideas. Furthermore, independent prep courses will likely concentrate on improving time management and efficiency skills.