The 70-431 exam is somewhat difficult to prepare for because it is broad in scope. This is not an exam that you can adequately prepare for by simply rote-memorizing terms and definitions. It requires you to analyze a scenario and answer problems related to it by combining various knowledge points from various topic areas. Successfully completing this exam requires thought and analysis to properly choose the best solution from several viable solutions.
The best way to prepare for this exam is by doing the work. You must work with the databases and all the related objects to be comfortable with the material the exam addresses. I also recommend that you leave no stone unturned. You should spend a considerable amount of time using SQL Server Books Online, a help facility that has a phenomenal amount of information. Another helpful resource is www.microsoft.com. In particular, you should visit the MSDN library site. These resources contain the answer to every question on the exam.