Retake the course in question. The new grade will replace the old.
Let the credits expire. If you had trouble in college right after high school and plan to go back as an adult student, talk to your adviser about limitations. Most credits expire after five to 10 years.
Take classes at a community college. Many program applications request a certain cumulative grade point average for acceptance. Taking prerequisites or electives at a community college raises that average.
Talk to your adviser. Often a bad grade in a general education course or elective will not affect your graduation requirement. Each school and program has different criteria.