While I have no experience with Maya in particular, the general strategy for debugging an addin is as follows: go into the Debugging properties for the project, set the startup type to "Program" (or something similar, depending on project type) and fill in the path to the Maya executable.

When you then press F5, VS will launch Maya for you and attach the debugger. When your addin is loaded, it will proceed to also load symbols for it. Breakpoints etc should work as expected.

This is the approach I use to debug AnkhSVN, which is a VS.NET addin.