The game tries to seed the AI homeworlds such that the distance between themsevles, the human homeworlds, and each other are maximized. This may sometimes mean seeding one AI homeworld closer to the player if putting both the maximum distance from the player would put them too close to each other. (like on snake maps)
This usually means you can try to find a set of connected planets that are the maximum distance from your homeworld, and the chance of one of the AI homeworlds being there are high. Things get a bit more complicated when there is only one such connected set, then you gotta start looking at connected sets that may be a bit closer to yourself but further from the other AI homeworld.
EDIT: Ninja'd
If you know some graph theory stuff, that can help out knowing ways to narrow down possibilities, though this is not really needed for high level play.