The first strategy I tried was simply randomness. It was pretty ineffective. A rule based one was also ineffective, as it tended to get itself into a box. But I found that adding a dose of randomness to the rule based strategy worked well.
Most computer strategies of the day cheated, or altered the rules to give an advantage to the AI. Empire didn't. I did have thoughts about creating an interface so people could provide their own AIs and then the various AIs could battle it out.
classicempire.com
There's been a lot of research on the Life game. But I bet Empire would be a much better research platform - the rules are simple, but the game play can get pretty complex. I had a lot of fun developing AI algorithms for it. I wish the ant algorithms were known at the time, I bet they'd help!
(One of the reasons the simple rules worked so well was the pieces had a hammer-paper-scissors relationship to each other.)