

This can be a little annoying (having to wait through a lot of saving screens) but it can also be worthwhile provided you are investing a lot of money to begin with. If the stock price goes down then reload your initial save game and try again.

Basically, it boils down buying and sell specific stocks before and after you complete the assassination missions for Lester (which are a big part of the single player story line). The "Lester Assassination Missions" method of investing in GTA 5's stock market is probably the most fool-proof method to make money in in the game, and lots of it too.
