If you've been an investor for any length of time at all, then you've almost certainly been advised to start (and maybe even finish) with index funds like the Vanguard S&P 500 ETF. This fund is of course simply meant to mirror the performance of the S&P 500.

Connect the dots. By simply holding a stake in the world's best-known market barometer, you're now only guaranteed to match its usually bullish long-term performance -- an average annual gain of just under 10% per year. But you're also more likely to outperform most other investors, including the professionals.

If you're new to investing and don't have a lot of money to get started, don't fret. The best place for new investors to begin is often with exchange-traded funds (ETFs), which will give investors instant diversification through a portfolio of stock holdings.

Vanguard is one of the gold standards when it comes to low-cost exchange-traded fund (ETF) options. Undoubtedly, passive investing (typically with index funds) tends to be wildly popular among the retail crowd.