First off, see getlibs, available here. This will determine missing libraries and install the appropriate 32 bit versions in the proper directory (Ubuntu: /usr/lib32 or /usr/local/lib32; Debian: /emul/ia32-linux directory).

Copy/paste of help:

Usage: getlibs /path/to/binary
getlibs -l i386librarytoinstall.so
getlibs -p i386packagename
getlibs -w www.website.com/i386package.deb
getlibs -i /home/jobriath/i386package.deb
See 'man getlibs' for more commands

--apt-file : Uses apt-file to find the packagenames for libraries. The default uses packages.ubuntu.com. This is especially useful for non-ubuntu users.

--build : converts a 32-bit package to a 64-bit package and installs it. This will only install libraries from a 32-bit package into the correct place! This will not install any binaries from that package! This is very beta.

--savebuild : use with --build. Saves new 64-bit package to /home/$USER

--mirror or -m : Use the specified mirror to download from if one is not specified for package

--verbose : Extra output

--ldconfig : Runs ldconfig on directories where new libraries are installed

-64 : Will let apt-get install 64-bit packages for a 64-bit system

-32 : Left only for compatibility with getlibs v1. 32-bit library installation is the default for all systems.

--distro : can set as either Ubuntu or Debian. Ubuntu installs to /usr/lib32 and/or /lib32. Debian installs to /emul/ia32-linux/

--release : can set as hardy gutsy feisty edgy or dapper. Determines what web interface release is used in search.