The main purpose of the TOEFL is for the university to make sure you will be able to comprehend the lectures and the course's written materials. Full university lectures are available online at Academic Earth (see Resources). Dedicate an hour or two every day to watch the lectures and take notes of the basic points, just as you are supposed to do as a student, as well as during the TOEFL listening part. Go to a library for this task, if there are distractions at home, such as kitchen noise, children's voices or the television. This exercise will help you especially on the second part of the test, the long conversations and lectures.
Listening practice tests can be found for free online--not exclusively on the TOEFL homepage--so don't miss the opportunity to test your listening comprehension abilities (see Resources). Exam English offers interactive listening activities where, similar to the actual exam, you will listen to a conversation or lecture and choose the right answer. On the other hand, 4English Exams gives you listening questions in written form, so that beginners can read the tasks at their pace.
Get in touch through your friends or on online social network services, such as Facebook. Explain why you need to interact regularly with university students and just start talking. Apart from practicing your speaking skills, listening to a student who lives in an academic environment for the better part of the year will prove invaluable. Especially for the first part of the listening test, which is comprised of short conversations, mainly between students, your experience will help you avoid mistakes.
Deep knowledge of English vocabulary is essential to succeed in TOEFL, but of course you cannot know every single word of the language. Listen to a lecture or conversation and write down every unknown word you hear, however you think it may be spelled. Don't let unknown words just pass by, even if you are able to find the right answers without them. During exam time, lots of terms you are not familiar with may be used and you won't have the chance to search for their meaning.