Currently Wheezy (testing) and Sid (unstable) are supported.
Squeeze isn't supported any more because Sugar is in the progress of migrating to GTK 3 / Gnome 3, requiring bleeding edge versions of a couple of components.
In order to install sugar-jhbuild, you need to install git-core, lsb-release, python and subversion:
sudo aptitude install git-core lsb-release python subversion pkg-config
After installing and updating sugar-jhbuild according to the common instructions, you can use this invocation to install all dependencies automatically:
./sugar-jhbuild depscheck -s | sudo xargs aptitude -y install
sudo apt-get install -t experimental gir1.2-evince-3.0 libevview3-3