Look for schools that offer accelerated degree programs. Some schools offer programs that are specifically designed to help students graduate in less time. You'll have to have a high GPA from high school or from any college that you've already started and you may also need some type of experience that can count toward your degree.
Talk to your college adviser about your goals. When you start college, your school will give you an adviser to help you plan your course work. Let her know that you want to graduate early and ask her for help in planning your requirements.
Test out of requirements. Some colleges have certain requirements, such as a foreign language requirement. You can often take a test to prove that you already have the knowledge necessary for this requirement.
Apply any credits that you have towards your degree. If you took AP courses in high school, you may be able to use those credits towards your degree. You can also apply college credits if you took some college classes before.
Load up your course schedule. Take the maximum amount of courses that your school allows each semester.
Take courses year round. Most students have a winter and summer break. You may be able to use those breaks to take on additional coursework. If your school doesn't offer a winter or summer program, look for those programs at other schools and ask if your school will accept the credit.