What are some basic rules for a successful yet temporary long distance relationship?

I'm gay, and my partener has had to move for work.. I'll be moving in with him in a month or two although it has already been 3 months... We are in a defacto relationship, yet when his moved away it's as though we don't even exist. It's a crappy break up waiting, but I would still like to know what other people consider a good long distance relationship.