My 2 cents' worth..
What I've heard is they're very strict about the answers in that even an extra a/an/number/word are considered errors. I've no idea if a human or a computer corrects it, but better not take any chances. Also, pay attention to the word limit. If they say not more than 2 words/numbers, that should be followed diligently. For eg., if the answer is "3 trips" do not put in "3 trips per day." Apparently, even spelling is very important.
For Listening, a good advice that I got from http://www.scottsenglish.com/ielts/ (free access I got when I enrolled for IELTS) is to read ahead 1-2 questions during each pause so that you know what you should listen for. While doing mock tests there, to my horror, I found that if my concentration digressed a bit, I couldn't keep up with the test anymore! So, identify your weak areas and practise those areas more.
@VIKAKUMA22, don't go for synonyms. The answers are usually what is exactly said.
@mahharrouf, do practise writing with a pencil because they insist on pencil for Listening and Reading. As an IT professional, I too found it daunting because we're so used to typing. For Writing, I used a pen, though. Do that only if you're confident of not making too many errors (too many strike-offs may be visually unappealing and create a poor impression). Better write out some essays/letters.
Oh.. in case you're wondering how I fared in my recent test, I scored overall 8.0 with individual bands of L 9, R 8, W 7 and S 8.
Good Luck to all!