The best strategy is to upgrade your corporation to the max.
Look for corporations that produce products that are short on the market.
the price will be high and with many upgrades, and high quality output, they will become very profitable and their market value will increase.
High tech corporations, and maintenance products are capable of very high profits.
Oil is in short supply and will be very profitable quickly.
Main point: upgrade the corporations and increase quality.
The welfare index is essential. it depends on health, education transportation etc.
If welfare is at 120 and salaries in corporations are at 400 level, corporations will produce at 120%. Profits soar.