The minimum list of packages to install to be able to run unstable-branch packages is below. Install these packages one at a time in exactly the order listed. When versions are mentioned, that is a minimum suggested version, any later version should also be acceptable.
While you can install many libc6 package with just ldso and libc6, you will probably want to upgrade a few other packages as well. Since bash-2.01 fixes problems experienced with Netscape and helper applications, it is one of the more likely packages to need updated. However, it is also one of the few packages that is capable of rendering your system useless if upgraded incorrectly. Install the packages below one at a time in exactly the order listed.
IMPORTANT: If you use dselect to do the initial upgrade of these packages, there is a very good possibility of breaking bash and therefore making your system unusable.
These packages are not absolutely essential for the functioning of the packages in unstable, but are still very useful. The new dpkg-dev may be necessary for unpacking source archives from unstable, and the new dpkg-ftp is needed if you wish to use the ftp method of dselect to upgrade your system to the unstable distribution.
Since perl is used in many package installation scripts, problems with with library upgrades may temporarily break perl, which may break other package installations. To be safe, install the new libgdbm1 and then the new libgdbmg1 packages by hand before upgrading perl.