Find an accredited university or college that awards the BS degree that you are interested in. Not all schools have every subject. An accredited university means that the school has proven to be a "reliable authority as to the quality of postsecondary education," according to the U.S. Secretary of Education.
Apply to your school of choice. You may want to apply to more than one school. Once you get into a school, apply for financial aid as well.
Participate in all of the required preliminaries such as orientation, placement testing and workshops. Some of these will be helpful in understanding what is expected of you and how to register for classes.
Plan out your goals for your entire school career. With a BS degree, there are usually a lot of math classes involved (unless your test scores are good), so you will want to spread them out over the semesters to make sure they get completed. Also, a lot of classes have prerequisites; this means that you will want to get these out of the way the first couple years of school.
Consult with your department advisor to be sure you are on the right track. This should be done every year. The advisors are also a good source of information about new classes and since some classes fill up fast, it's good to know early.
Finish your classes by getting grades in acceptable passing ranges. Some schools require a B or C average to graduate.
Make sure you meet with all of the requirements for graduation. Complete all required classes, residency requirements, credit requirements and deadlines. Apply for graduation by the school's deadline; this could be a semester or a year before your graduation date.