My attempt at installing Spam Assassin was pretty dismal. Using info from the DH Wiki and from Spam Assassin just was not enough detail to get it working. I ended up using Gmail double-pass filtering which was incredibly easy to get working. Gmail's spam filtering is exceptional. You may get a few false positives at first, but they are easy to tune.
I spent several hours trying to get my own Spam Assassin working but only 30 - 40 minutes getting Gmail filtering to work.