The Bogleheads' Guide to Investing

Start early and invest regularly. Know what you’re buying. Preserve your buying power. Keep costs and taxes low. Diversify your stock portfolio [and diversify your stock risk with a bond portfolio].”

As a group, we investors are inevitably average, so beating the market is a zero-sum game. (After our investment costs are deducted, of course, it becomes a loser’s game.)