Below-average fees and superior long-term returns make these funds good bets.

With thousands of options to choose from, selecting the right mutual fund can be tough. While past performance is no guarantee of future success, one of the most proven strategies is selecting funds with solid long-term track records. Managers of these funds tend to invest for the long haul instead of making shortsighted bets or chasing the latest market trend.

Using our exclusive U.S. News Mutual Fund Score. we’ve compiled a list of the best long-term performers in some of the most popular mutual fund categories. Over the past 12 months, every fund on the list has received an average U.S. New s score of 7 or higher. Our score is based on the ratings of some of the mutual fund industry’s best-known analysts, including Morningstar, Lipper, Standard & Poor’s, TheStreet, and Zacks.

To gauge performance, we screened our database to find funds with the highest 10-year trailing returns as of the end of March. Each fund on the list finished in the top quartile of its respective Morningstar category, with the exception of a few index funds, which we’ve included as options for investors who favor a passive investing approach.

[See top-rated funds by category ranked by U.S. News Mutual Fund Score .]

Since high fees can eat away at long-term returns, the funds selected for this year’s list charge annual expenses that are less than their respective category average. In the name of affordability, the funds also have minimum investments of $25,000 or less.

For those who prefer passive investing, we added a number of index funds to this year’s list. Many investors forgo actively-managed funds—the majority of which fail to outperform their peers over time—and opt for index funds, which track the performance of indexes like the S&P 500. A few of these index funds didn’t finish in the top quartile of their category over the past 10 years, but we added them because they give investors low-cost exposure to a wide range of asset classes.

Some funds were left off the list if they frequently change styles or employ specialized strategies that may not be appropriate for long-term investors. Funds that were closed to new investors were also excluded, as were funds without 10-year track records.

This year’s list includes a few new categories. World allocation funds—also called go-anywhere funds—have grown in popularity, and three of them made our list. While many fund managers are limited to investing in a particular size of company or slice of the market, managers of go-anywhere funds have the flexibility to invest across multiple asset classes such as stocks, bonds, and commodities throughout the world.

Domestic stock funds were screened by market capitalization and Morningstar style box. Each market-cap category (small, midsize, and large) includes a relevant index fund. Two broad-market index funds, Vanguard Total Stock Market Index (symbol VTSAX) and Vanguard Total Bond Market Index (VBTLX), were also added. These funds give investors exposure to the entire range of stocks and bonds in the United States in two simple investments.

Foreign stock funds were chosen in a similar fashion, and our list includes a mix of market caps and styles. Four foreign large-cap stock funds were added along with one fund that specializes in smaller foreign stocks. One actively-managed diversified emerging markets fund, Oppenheimer Developed Markets (ODMAX). made the list, as did the passively-managed Vanguard Emerging Markets Stock Index (VEMAX). A single world stock fund, which invests in stocks throughout the world, including the United States, rounds out the list: Oakmark Global (OAKGK) .

Four balanced funds, which invest in a mix of stocks and bonds, were also included. Two Vanguard funds, Vanguard Wellington (VWELX) and Vanguard Wellesley Income (VWINX). made our list. The managers of the Wellington fund invest about 60 percent of its assets in stocks and the rest in bonds, while the managers of the Wellesley fund invest more heavily in bonds. Permanent Portfolio (PRPFX) also made the list, in part because of its unique strategy and holdings, which range from hard assets like gold and silver to currencies and treasuries.

Two speciality funds were also added, Cohen & Steers Realty Shares (CSRSX). which invests primarily in real estate investment trusts (REITs), and Van Eck Global Hard Assets (GHAAX). which specializes in natural resources like precious metals and commodities. These asset classes have seen plenty of interest from investors concerned about the threat of inflation.

On the fixed-income side, four intermediate-term bond funds were included. TCW Total Return Bond (TGLMX) tops this year’s list of intermediate-term bond funds, thanks to its outstanding long-term performance, although a sudden management change in late 2009 leaves it a bit untested.

A few bond funds that serve more supporting roles were included. Loomis Sayles Bond (LSBRX) and Fidelity Strategic Income (FSICX) are both high-performing funds that invest in a range of fixed-income asset classes. Two high-yield funds also made this year’s list. The managers of these funds invest in high-yield bonds—sometimes referred to as junk bonds—which are considered more risky than investment-grade bonds like treasuries. However, they also provide a higher yield in return for that additional risk. A short-term bond fund, Vanguard Short-Term Bond Index (VBIRX). was also included. The fund’s returns were mostly in line with other funds in its category, and its rock-bottom fees give it a leg up in a low-yield environment.

Here is the full list of 50 funds: