70-536 is a good exam that covers the Framework Libraries. If you have experience in developing applications under the .Net Framework 2.0 you are well positioned to take this exam.
However, even if you do have experience, you should still read the list of topics covered by the exam and look up each of them in MSDN to make sure that you are not missing anything. For instance, you may have been developing applications for three years
without ever having had the need to use a CryptoStream; you should then look up how it works so that you are prepared to answer the exam questions on this subject. Similarly, study all of the topics tested by the exam with which yu are not already familiar.
The list of skills tested can be found here:
http://www.microsoft.com/learning/en/us/exam.aspx?ID=70-536&locale=en-us#tab2
If you are not confortable enough looking up the topics in MSDN, you may want to buy the self-paced training kit, or maybe take courses 2956 and 2957. These and other preparation resources are listed here:
http://www.microsoft.com/learning/en/us/exam.aspx?ID=70-536&locale=en-us#tab3
