Now that there are an increasing number of boards running in 64 bit mode (Aarch64) it might happen that you want/need to run a 32 bit application on a 64 bit OS. I suspect that there is more than one way to do this, but here's what I've been using:
dpkg --add-architecture armhf
apt-get install libc6:armhf libstdc++6:armhf
Some applications need the following step to run:
ln -s arm-linux-gnueabihf/ld-2.23.so ld-linux.so.3
There is a downside to this approach - after adding armhf you have to be careful when installing new packages that you get the right version and don't end up installing 32bit packages that you don't need.