[raynor]

Start a game on a large map so you'll have some expansion room before you encounter the first AI. Then try these:

1. Expand as quickly as possible. Because colony ships are so cheap, I use them instead of warships as scouts. You want to colonize everything in sight. You should always have at least one colony ship under construction and another one in space headed someplace.
2. If you encounter a system with an AI colony in it, don't put a colony there, and don't send your ships through this system. Pretend the warp point leading into that system is a brick wall.
3. Make treaties with everyone you meet but don't let them have a Military Alliance unless you don't mind them colonizing planets inside your system.
4. Research Construction, Mines, Warhead I-III.
5. Put a mine field at every warp point leading into your system.

At any level of difficulty, mines are absolutely deadly to the AI. After encountering a mine field for the first time, the human player hopefully would be smart enough to sweep it before sending any ships through. But the AI isn't coded to do that.

For the ultimate in protection, you can research Astro Physics and then Stellar Manipulation until you can build the component on your ships that closes wormholes. Unless the game Lasts really, really long, the AI isn't going to open a wormhole into system where you've closed off the wormhole.