First things first! You will need a passport that doesn’t expire too soon -- at a minimum it should last for 6 months after your anticipated return from your study abroad program. Apply or renew now if you need to!
Important: Make sure you sign your passport before travel, as it's not a valid document without your signature!
Visas and Permits to Stay
Summer or Semester Study ONLY
For U.S. citizens studying in the United Kingdom for a summer or a semester term with no internship, a visa isn't required, but it's essential to apply for the ETA at least 10 days before your flight. You can do that by visiting this link and filling out the relevant information. It costs £16 and is valid for 6 months.
Year-long Study ONLY
For students studying abroad in the UK for an academic year, a student visa is required. The application process is online, but applicants must go to a biometrics facility for fingerprinting and a photo. Avoid international travel before the study abroad program begins, as mailing your passport for the visa application is required.