At the beginning of the game, make sure the game speed is not too fast.
Go to the stock market and buy # 4 million shares at any of the refineries.
After a while, you will notice that the stock price began to rise sharply.
Sell them ASAP and buy more at another refinery. Later,
repeat this process and save up money. When you have enough money,
buy as many shares as you can afford by May or June in the first year.
Then, every three months you will receive dividends.
Sometimes the value of a stock can go up dramatically. If it happened
(most often this happens when loading a save), then buy
as many shares as you can. Then the share price can
increase by the thousands. Sell them immediately and keep repeating
this as long as your bank balance allows you.