Fill out your application in full. You can fill out the Common College Application (see Resources) or the applications provided by the schools you wish to attend. You also have the option of filling out paper or digital applications. Some schools will waive the application fee if you apply online. Check with each school's admissions office for details. This is one of the easiest parts about applying to school. The applications typically ask for a great deal of information about you and your family and tend to be fairly self-explanatory.
Have your AP/IB, SAT and/or ACT results sent to your potential schools. When you take these exams, there will be a section that asks for a list of schools to which you want your results sent. Each school has a specific identification code you'll use for this section; you'll be able to browse a list of schools and their codes before or after your exam.
Write your personal statement. This is generally considered to be the most difficult part of the application proces, but don't be intimidated. Most universities present you with a broad writing prompt that asks you to explain why you feel you're a good fit for the school, tell a story of personal achievement or explain how you overcame adversity. Approach the personal statement like you would an important exam. You should be well-fed and rested before you start writing and you should choose a quiet, comfortable location in which to write. Free yourself from distractions and keep the prompt in front of you to help stay focused. Have a teacher proofread your paper before you submit it.
Gather all of your application materials. You'll need sealed, official transcripts from your school, recommendation letters, the application, your personal statement and the application fee (if applicable). Most applications come with checklists of the materials you'll need to include. Double check them to make sure you don't forget anything. Pack everything into an envelope and send it to your school. If applying online, you'll still need to mail some materials. You may also be able to fax some materials directly to the admissions office. Check with each school for their policies on receiving applications.
Check with each admissions office to make sure it has received all of the required paperwork. Some schools will call or email to inform you of any missing forms or materials, but this isn't universal; take every precaution when applying to schools and make copies of everything you include in your application packet. Once you're sure each school you've applied to has your full application packet, it's time to wait for their respective decisions.