Below is a Quora question I once answered with the title of this post being the question asked. The answer below is unedited and just as answered
Look at it this way, being rich (done honestly) is a by product of something. That something is offering a service which is needed in the most satisfactory manner possible. Thus, thinking about how you will become rich is like putting the cart before the horse. Instead, think about how you can offer the best service possible and the rest will flow.
Look at it this way, Bill Gates of Microsoft and Jeff Bezos of Amazon are among the richest men in the world. How did they become rich? They became rich by offering a service badly needed by millions (if not billions) and did it in a way that was never before done. Run this thought experiment: if for some reason Amazon and Microsoft fail to exist tomorrow, how will change the world? Would consumers be happier or unhappy? Would their standard of living drop in some day? If your answer revolves around the idea that these companies offer a service many can’t do without, that should give you an idea why these men are as wealthy as they are!
Focus on the service and everything else will follow!