An index fund is a fund that simply invests in all of the stocks in a market. So, for example, an index fund might invest in every single stock or almost every single stock in the U.S. market, it might invest in every single stock abroad, or it might invest in all of the bonds that are out there. And you can make a perfectly fine investing portfolio that mixes equal parts of all three of those.

You have to ask yourself, what are the things that matter to you most in your life? If you have to have a latte every day that'snice to have right now, but if you take that latte every day right now, you may wind up eating cat food when you are 70. And you have to decide which is worse.

All the things that make us human make us terrible investors and you have to understand what they are and how to avoid them.

The key thing about any fund is to make sure its expenses are low. You know, if you look at the funds in your plan and you see that they're all charging 1.5 and 2 percent,you've gota bad plan.

While it is probably a poor idea to own actively managed funds in general, it is truly a terrible idea to own them in taxable accounts... taxes are a drag on performance of up to 4 percentage points each year... many index funds allow your capital gains to grow largely undisturbed until you sell... For the taxable investor, indexing means never having to say you're sorry.

It's bad enough that you have to take market risk. Only a fool takes on the additional risk of doing yet more damage by failing to diversify properly with his or her nest egg. Avoid the problem-buy a well-run index fund and own the whole market.

When it comes to fund managers and market strategists, this year's hero usually turns into next year's zero.