Alberto, here are some hints if you want to improve this part of GNOME (ie, reduce the technical level needed by newcommers to just become jhbuild users).

- Create a standard .jhbuildrc for newbies.
Look at http://live.gnome.org/JhbuildDependencies
But a jhbuildrc is a bit distro dependant... For example, I maintain the Mandriva subsection:
http://live.gnome.org/JhbuildDependencies/MandrivaLinux

- Create a metapackage gnome-jhbuild-essentials:
This may not work, as dependencies vary from each GNOME version to build. You'll need a gnome-2.16-jhbuild-essentials and a gnome-2.18-jhbuild-essentials.

- Create a page on the wiki for newcomers, explaining howto setup the enviroment, play with module sets, and create a patch.
I was working on a new jhbuild guide this some time ago, but didn't finish it, so you can modify it if you want.
For patches, a patch submission guide exists, but needs some update for the cvs->svn migration:
Relevant content of Elijah's guidelines need also to be imported, as this kind of info should now be centralized in the wiki (Elijah was ok with this, I talked to him about that at last GUADEC).

Check also:
http://live.gnome.org/CategoryJhbuild
http://live.gnome.org/CategoryJhbuildIssues

Enjoy ;-)