I used lot of exam material from UML 2 Certification Guide: Fundamental & Intermediate Exams (The OMG Press) by Tim Weilkiens and Bernd Oestereich. Great book though book expects you to know UML first. So I did my basics from various sites. It took about 2 weeks to prepare. Didn't buy any practice exams available.
Some questions were tricky, well, they has to be otherwise whats the fun