I took my test on 12th December (London) and my results were available online on 28th December. For those interested I scored: Q168(96%) V163(93%) AW4.5(72%) The unofficial scores displayed at the end were exactly the same as the official ones, and this seems to be the case for most people.
There were two good pieces of advice that I received: 1) focus on the section you need, and 2) ignore all other generic advice! You can only focus on the way you personally like to study, and there are no shortcuts around that. You know deep down when you understand a topic, and you know when you don't.
My own strategy was mainly dictated by time constraints, so I set aside about ten days before the exam to read up on it (a couple of hours per day, after work). I was only really taking the test for the Maths element, so I 'revised' Maths stuff and took three or four practice tests, and I took a practice verbal test just to get a feel for the format. Taking a practice exam early on in the revision period was quite helpful to me, so may be the case for others too.
I only had two prep guides (GRE and Barrons) and I found them both useful for quantitative practice questions, though probably found Barrons the more useful of the two. I didn't practice the analytical writing but I wish I had done, just to get a feel for the timing. The clock seemed to run down quite quickly on the day, and it was a rush to finish the first one.
A final thing that I found useful was the 'review' function for the Maths - dwelling on a question could ruin the whole test! Otherwise I think you just have to be a confident and as calm as you can, and you will get a result that you are happy with.