Well, were to start:
-Reduce requested Quality to about 150-170
-Set Trading Strategys to 'Best Price' Buying as well as selling
-Stop building Corps on unprofitable fields, for example: You have 3 new Airplane Corps and there is allready a huge Surplus of Airplanes on the market, meaning low Prices, meaning small to no Profit
-Wait for Corps to be fully upgraded
-Close Corps that are highly unprofitable or if you believe their Resources will be on high demand in the future at least put down hiring as Long as there is no Profit to be made, Product Groups that are often unprofitable even if they are in high demand are afaik Agricultural, Food products, strategic Forces Corps
and last but not least: post on 'help' forum