I reckon the most important thing in exam preparation is not to get worried if you can't do the hard questions, because you can still get a very good mark if you've got a solid grip on the basics.
In other words, try not to underestimate the importance of some of the easier topics because they are still worth a large portion of the paper. For example, integration and graphing are very easy, and so often I find I overlook them to concentrate on the harder topics like conics and mechanics; and I could risk losing easy marks if I have not revised them thoroughly.