This is my personal investing manifesto, written in a do's-and-don'ts format. Roughly 90% of my household's investable assets reside within 401(k) plans, IRAs, or 529s. The remaining 10% is in a rainy-day fund, currently earning just over 2% per year in an online savings account. In amassing and managing these assets, I adhere faithfully (most of the time) to these basic principles.
1) Save. You can't invest money until you've saved money. Saving is all the more important in the context of the depressingly low expected returns we face today. The market likely won't do the heavy lifting for you over the next few years, so you will have to shoulder more of the burden.