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There were two classes specifically about Subassembly Composer at Autodesk University 2011:
There were two classes at AU last year on this, one by myself and a very detailed class by Kati Mercier that you should check out. We both did an hour of how to get started with Subassembly Composer.
We also have a number of sample Subassemblies on the Help Wiki site that you could look at for starting points.