1. Be very lucky
    Win the lottery, get a job as a chef at Google in the 90s, etc., etc. Narrowly beats out being born rich because you appreciate it more! Can also be incredibly easy.
  2. Start that way
    Be born that way. And then don't screw it up. Great because all you have to do is show up and bite down on the silver spoon.
  3. Own things and then have them become (much) more valuable.
    Like start a business. Or real estate. Or stocks. Would be #1 except that it's so hard. Most potential to make most money. Also comes with power and respect and can be rewarding.
  4. Be the best in the world at something that is worth a lot of money to people
    This one is tricky because you need to be amazingly good at the right thing at the right time and for a long time to really make a lot of money. Kevin Garnett is a great example of this.
  5. Rip off other people
    Surprisingly hard and the payoff isn't usually that great. Like, Bernie Madoff could have made a ton of money taking a few points in management fees and putting all his clients money in index funds. Why bother with all the stress and the shame?