Take note of the economy of every space station you encounter. Each colony specializes in a particular commodity, and will buy specific cargo at higher prices. Purchase extracargo at stations where the commodity is cheaper, then travel to stations where that product is in higher demand.
Enter a Low-Intensity Combat Zone and scan it for NPCs that are wanted or from an enemy faction, all while avoiding other players. Destroy lone ships to earn money.
Search for discarded containers, especially those that contain gold that can be sold on the Blackmarket.