Making 32-bit .debs for 64-bit systems

[Nolan Check]

I use an amd64 system, but some applications are only available for the i386
architecture. Some prominent examples are Adobe Flash, Google Earth, and
zsnes (which is written in assembly language, so I don't reckon to see it
ported EVER.)

I can usually get these i386 programs to run, but they require 32-bit
libraries. ia32-libs has a whole bunch of i386 libraries for amd64, but
it's not a complete solution. I recently had to install a 32-bit libselinux
and libsepol to get Flash to run; they weren't included in ia32-libs. I did
this by downloading the i386 .deb from packages.ubuntu.com, extracting the
package, and manually copying all the files from the package's "/usr/lib" to
my "/usr/lib32". zsnes requires a 32-bit libsdl, which I also have to
manually install.

Are there any guidelines for creating .deb packages to install i386
libraries on amd64 systems? Is it enough to simply map /usr/lib
to /usr/lib32 or are there other complications I need to deal with?