Just read this booklet and it outlines five pitfalls for young people:
1 failure to save
2 ignorance of financial theory
3 unawareness of financial history
4 dysfunctional psychology
5 the rapacity of the investment industry
So to counteract, he advises to max out retirement, study finance, know your history so you won't repeat it, know yourself, and protect yourself from the investment industry.
He goes into greater detail and forces you to do your own research, but overall a great read for Millennials who want to get started with investing.
Remember start early and COMPOUND ON!