I recently gave TOEFL and just got my score. I was pretty surprised as I was expecting something in early 100s but got 113. (R-26, L-30, S-28,W-29)
Something about me- I am not a native speaker of English, however I would rate myself as average in English. I prepared for 2 weeks, and during that time diligently for the last 2 days, concentrating only on TOEFL (I am also preparing for GMAT).
Resources I used and did not use:
1. I did not register for any coaching/tuition/guidance services. My thinking for the same was because TOEFL itself is a 170 dollars exam and an addition 100 dollars for some coaching was not affordable. This is a personal opinion. I have seen my friends getting outside well and performing equally well. So, each his own.

2. I accessed and followed some online free TOEFL help sites. The best was Notefull. I registered for the free course. They provide comprehensive videos. I watched all the parts minimum of two time. This helped me get a fair idea as to what to expect in the exam and also the tips and strategies that they provided were very useful. Highly recommended!
3. Try Free mock TOEFL online tests. Proved really fruitful to me. Got me into the mode and the experience of understanding what I should expect and helped me practice.
4. Cambridge TOEFL Guide- Really helpful. But I just practiced Speaking part from the last CD. This book is great because it provides 7 practice test.
Advise:
Familiarize yourself with the pattern of the exam.
Practice! Practice! Practice!
Check on what basis are the writing and speaking sections marked and practice accordingly.
Finally, believe in yourself and have faith. You will do well on the day of the exam!
All the best!