We have a tool called "jhbuild" that keeps track of all the dependencies and stuff. In short, just get jhbuild from git.gnome.org, build it and do a "jhbuild bootstreap && jhbuild build".

More complete instruction can be found in the wiki: https://live.gnome.org/Smoketesting

If you want to just check out gnome-shell without the other Gnome 3 stuff, you can find instructions on http://live.gnome.org/GnomeShell

If you want to get started with Jhbuild, you probably want to have a look at the official manual:

  http://developer.gnome.org/jhbuild/stable/

If you really want to build the whole thing for hacking purposes, yes, Jhbuild is probably what you want.

But if you just want to give GNOME 3 a try, I suggest you to simply run one of our live images here:

  http://www.gnome.org/getting-gnome/