Review the basics. Grab an English grammar book and a tutor or an English speaking friend, and make sure you understand basic English grammar. College level English will involve a bigger vocabulary and more complex sentence structures. Have a tutor help you with subject, verb and object agreement and other simple parsing structures.
Use English daily. Practice your listening skills by watching television or listening to the radio. Communicate with people by talking to friends, ordering from a restaurant and talking with a tutor. Read newspapers, study magazines and books. Start off with simple children's books to help gain confidence and build the complexity and length of reading materials as you go along.
Practice with TOEFL example questions. To get an idea of advanced English test questions, work through practice exams. Look up words you don't understand in a dictionary. Make flash cards of vocabulary terms or grammar descriptions. Keep a list of higher level words handy and incorporate them in everyday usage.
Get corrected. Have a tutor or close friend help hone your English skills by listening and adjusting your pronunciation. Watch the English speaker move his lips, tongue and teeth when forming words. Practice in front of a mirror to replicate the same movements.