Currently squeeze (testing) and sid (unstable) are supported.
In order to install sugar-jhbuild, you need to install git-core, lsb-release, python and subversion:
aptitude install git-core lsb-release python subversion
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