This may seem like common sense, but I just tried it a couple times and it really made the game more fun.

A frequent problem seen with Korx, Altarian, and Terran opponents is that they take too long to build offensive ships, although they may load up their starports with transports. If you use the scenario editor from the latest version of ToA, you can edit the races' starting technologies. I gave everybody their default starting techs, plus the military techs up to and including Space Weapons. In my last game this seemed to have a leveling effect with the result that a couple of races that normally don't do very well (Korx and Iconians) ended up being my biggest rivals (I was playing as Terrans).