My favorite tactic was to monopolize SmithOre, and then buy/release all the MULEs so everyone after me couldn't build anything. Apparently a need for MULEs causes SmithOre to skyrocket.
So I sold food energy at a higher pricepoint than the ore. Often the AI players couldn't afford food / energy anymore and therefore their production collapsed and they did not have enough food to have enough time to change the installations on their plots.