Just got my TOEFL results, 118 out of 120, lost 2 points in the speaking section.
I've never had any problems with english, but after my GMAT experience (got a 750 on the eve before the exam and on the real thing got a 710) I decided not to take any chances. I took the TOEFL on a Saturday and spent from Wed-Fri at night studying for the exam.
Reading section >>
This should be one of the easiest, specially if you have already studied for the GMAT. Just don't waste time reading the whole thing before answering the questions, skip rightaway to the first question and if it's a specific question regarding the meaning of a word or something like that go straight to the right answer and don't lose time. Normally only the last question in each reading requires for a full understanding of the passage.
The session is rather easy in the end, just be careful with timing
Listening >>
I've listened to the practice questions on the sample exam ETS provides. It's rather easy, but you have to be careful not to lose focus during the passage. A good way I found to avoid this was to keep notes of everything in the order it showed in the passage. For most of the questions you won't use your notes, but it's a good solution if u tend to get distracted.
Speaking >>
This is where I spent some hours studying for real. Learn the structure of each question and how to structure your answer, these videos are great for this, but you also should be prepared for some small variations. Try spending some of the extra time in the reading/listening sections and also the break to prepare your answers for this part.
Also, this is a great website for practicing
https://www.eng1on1.com/ibt.php?test=1Writing >>
Same as AWA on GMAT, learn the structure you are using for each of the questions. The videos above should be enough. Try also to spare some free time to prepare your stucture ahead during the break or some extra minutes you get in the first sections.