Always try to corrupt, enslave, build a black market, bribe, etc. any possible planets. This gives you sight on the planets base and units, not to mention many credits. This will also make your game much easier.
Easy Zann Consortium Galactic Conquest
If you play the Empire in Galactic Conquest or multi-player mode (most likely) with the opponent with the Death Star (II), Corrupt all their planets. Iin multi-player mode, look for the Death Star (II) on planets. Make sure you have the 38,000 credits to destroy it first then sabotage it so that the planets are still alive. When sabotaged it cannot be constructed again.
In space battles as the Empire, put an Interdictor cruiser in the little box when organizing a fleet. By doing this you can send in your forces to a battle and stop enemy ships from escaping to hyperspace using only the Interdictor. When your opponent attacks the lone Interdictor, hyperspace in your reinforcements directly on top of them. Imperial Star Destroyers work best for this and provide a big surprise to an enemy player.