Be cool buddy..Based on ur post, I can infer that u've been to a good English studying background. Toefl iBT is about measuring ur English language ability in a general environment. What I'd suggest u
1. Reading session: U will be getting 3 passages to read and . U maybe given a combo time for all of them, or the time cud be divided for each passage. So, be careful about the time. My advice is check the question first, and don't spend time in reading entire passage at once. It wud be a waste of time, because they tell u which passage contains the answer. By the time u answer the questions, u will already get to know the complete passage enabling u to answer the conclusion question.
And yeah, don't miss any questions because not answering questions costs u some marks.
Not to miss: In one question, they ask u about the nature of the passage. Be informed about different natures or passage beforehands.
One more thing: Do not panic, passages are usually easier.
2. Writing:
Shudn't be grammatically incorrect. Do not write uselessly complex sentences. British or American English, both are correct. To save some time, please look at some toefl ibt essays u can find online, that will help u develop a pattern for essays. And yeah, good typing skills is always a plus point. I guess u already have them. After u complete ur essays, please substitute some common words with good vocabulary words to let them know that u've got a good vocabulary.
3. Listening:
For me it was the easiest one. Go thru a couple of films, CNN and English serials.
4. Speaking:
This is where we are bound to have problems. Universities usually look for Teaching Assistants with good spoken English. I had problems with that. I thought that I speak good English, but came to US and found that it was just Nepali version of English.
Quick tips about speaking:
a. Speak slowly, clearly and loudly, trying to pronounce each of the words completely.
b. There are few questions that appear everytime, I forgot the questions but I guess u know them. Get good answers for them rite now so that u don't have to waste time in thinking.
c. I wud like to add up again, do not speak in a hurry. Speak calmly taking ur time.
d. Good grammar, add few good words at times to show ur vocabulary.
e. Do not use hmm.. like or filler words too often instead of that take ur time to speak up calmly taking ur time.
g. I wud recommend u not using slangs and terms like gonna, wanna etc.
Hey, was it any useful lemme know.
Best of luck!!