First teach the system about 32bit packages: sudo dpkg --add-architecture i386
Then, bring the system up to date: sudo apt-get update; sudo apt-get upgrade
Download the latest version of CrossOver: wget http://crossover.codeweavers.com/redirect/crossover.deb
Install CrossOver: sudo apt-get install gdebi; sudo gdebi crossover.deb
or sudo dpkg -i crossover.deb
After this, CrossOver will be installed but it will be missing various packages. Install them now:
"Title"="Missing 32bit libOSMesa.so.6 library"
"Description"="This is needed by some games and CAD-like applications to perform off-screen rendering."
"Title"="Missing 32bit libtiff.so.4 library"
"Description"="This is needed by some applications that need to manipulate TIFF images in their user interface."