Index investing means buying a fund that owns a slice of the whole market instead of trying to pick winning stocks, and most professionals fail to beat it after fees.

A single share of a broad index fund gives you instant diversification across hundreds or thousands of companies.

Choose your first fund by cost, breadth, and fit: look for an expense ratio under 0.1 percent and a fund covering as much of the market as possible.

Invest regularly and automatically on payday, which smooths out market ups and downs and removes the temptation to time the market.

After buying, do nothing most of the time: keep contributing through downturns, rebalance yearly, and ignore daily market noise.