Master of Orion: Conquer the Stars/Expansion

Basic Colonization Expansion
You build up a fleet of the strongest war ships available. Example: 3 each Destroyers

Then you send the fleet to an unprotected system - typically adjacent to your territory. Send each ship to an outbound warp point and set them into guard mode.

Afterwards, send a Colony Ship and Space Factory to the guarded system. Colonize the best planet. Get the Space Factory to build Military Outposts at each guarded warp point.

Once the outbound warp points are protected by a Military Outpost, gather up your war fleet and repeat.

If the lane to this system is protected at the last system, scrap the Military Outpost as it will no longer be needed.

Some Suggested Colonized System Structures
For a colonized system which has an asteroid belt and / or a gas giant planet (while the Space Factory is in the system):
 * If the system has only one of these options, build credit generating structure (like an Asteroid Mine or a Superscaler Gas Harvester)
 * If both options are available in the same system, build the Superscaler Gas Harvester (for credit) and an Asteroid Laboratory (for research points)
 * If the system has two asteroid belts, build an Asteroid Mine (for credit) and an Asteroid Laboratory (for research points).

Blockading
As your Scout ships map out the various planetary and wormhole systems of the galaxy map, make note if you encounter other opponents. Using the Basic Colonization, claim the systems, one planet at a time, with the objective to block expansion by the opponent. Certain races are expansive, notably Meklar, Klackon, Sakkra. If you can block these races before they can expand too much, then controlling the diplomatic exchanges will be easier. As an extra bonus, if they happen to have an Antaran asteroid system, you can seize control of said system to help achieve the Antaran Victory condition.