There's no magic answer. One isn't enough, because that school might not admit you. More than ten might be too many, because applications take a lot of work and you need to do a great job on every one. Also, most schools require application fees, so costs can add up. (Note: many schools waive fees for low-income students.)
Fast Fact: Applying to a few schools that really interest you is better than applying to as many as you can.
Every college has its own application requirements. Different programs within the same school may even request different items. Learn exactly what your school needs by checking with their admissions office or going to their Web site. Start preparing well before the application deadline. Check and double-check everything before you submit.
Applying early can sometimes give you an advantage. At some schools, a higher percentage of early applicants are accepted. And if you do get early acceptance, you can skip a couple months of stress and uncertainty. You can also get a head start preparing for your freshman year. But applying early is not for everyone. Here's the lowdown:
Here's some general application advice: