1) don't get married
2) don't have kids
3) don't get addicted to anything (drugs, alcohol, food, gambling, etc)
4) don't go in consumer debt
That's a good start.
Pretty much.
For most of my career i've saved or invested over 50% of my salary per year.
I also live like a cheap ass except for certain things.
Drive old cars, wear normal cloths, buy off brand items, etc.
I still shop for sale items at certain stores. You can save $500 a month easy if you just shop smart.