I used "Querying Microsoft SQL Server 2012 by Itzik Ben-gan; Dejan Sarka; Ron Talmage". It's pretty compreshensive, has exercises, a cd with practice tests and exam simulation etc. I would say the test was significantly more difficult than the practice tests.

Of coure T-SQL is a very broad language so each presentation of the test could be completely different. In my case, there were plenty of questions about xml. You should know xml raw vs auto vs path very well. Seems like MS is very proud of this functionality and push it in testing. Lot's of questions on Views with Schemabinding for some reason. Plenty of questions about Ranking...rank vs dense rank vs row_number. Know how to write these for sure. Merge into also made an appearance or two on the test. There are 14 new functions in 2012 so I would definitely become familiar with all of them.

Again, I was surprised how heavily xml, views with schemabinding and rank/row_number functions were represented in the test, but your experience could be nothing like mine so get a good handle on every concept you can before taking it.

A good thing about using a training kit like the one I listed above is that by taking the self tests you can see where you weak and go explore other resources to build your knowledge.

Don't be nervous, just do your best and everything will be OK.