Take the SAT or ACT and score at least a 1250 or 28, respectively. Put particular emphasis on the verbal section of the test.
Research schools with top-ranking English departments in the area of your interest. A school with a well-known British literature department might not have a great creative writing department, so be sure to investigate the particulars.
Apply to six or seven schools that you've researched and chosen.
Claim you major as English and meet with an adviser to discuss your class requirements. Some undergraduate programs require you to complete a reading list prior to earning your English degree, so find out requirements ahead of time.
Take the courses suitable to your area of interest. In creative writing, this requires introductory classes in poetry and prose writing. In literature, your course load probably covers the entire period of English literature as well as classical literature. As a junior and senior, you can take seminars that focus on particular authors or schools of criticism.
Write an undergraduate thesis if your department offers it as part of your English degree. The thesis can be used as a writing sample for graduate school applications and prepares you for long writing projects.