Xdoclet has a big variety of tags, so it really depends on your needs (and what exactly you wanna do).
You could take a look at
http://xdoclet.sourceforge.net/ for general info and come back later with some specific questions.
Also, there's a nice tutorial at
http://tusc.com.au/tutorial/html for lomboz(xdoclet plugin) and eclipse integration. You'll find a some xdoclet usages overther.