You can invest in all three major asset classes — stocks, bonds, and cash — through mutual funds, which pool your money with that of other investors. Each mutual fund is managed by a professional who selects specific securities to buy, based on a stated investment strategy.

Mutual funds offer two major benefits. First, they provide greater diversification because most funds own dozens or even hundreds of securities, reducing the risk compared to buying a few individual stocks or bonds on your own. Second, they offer the expertise of a professional fund manager, whose skill in selecting investments is part of what you pay for when purchasing shares of the fund.

A mutual fund may focus on one asset class or combine multiple classes. For instance, a balanced fund typically invests in both stocks and bonds, while a lifecycle or target-date fund adjusts its investment mix over time, becoming more conservative as its target date approaches. Actively managed mutual funds seek to outperform a benchmark index, such as the S&P 500, through strategic buying and selling of securities. In contrast, passively managed funds, also known as index funds, aim simply to mirror the performance of a specific market index by holding the same securities included in that index.

Before investing in any mutual fund, it is important to carefully review its investment objectives, risks, fees, and expenses, which are detailed in the fund's prospectus. This document, available from the fund company, should be read thoroughly before making any investment decisions.

Like index funds, exchange-traded funds (ETFs) typically invest in a basket of securities that represent a specific market index. Due to their structure, ETFs often have lower expenses compared to actively managed mutual funds. Additionally, unlike mutual funds, ETFs are traded on exchanges throughout the day like individual stocks and can be purchased on margin.

Choosing the right combination of investments is just as important as selecting the specific securities themselves. The mix of asset classes — stocks, bonds, and cash alternatives — largely determines a portfolio’s overall performance and its fluctuations over time. This balance is referred to as your asset allocation. While it does not guarantee a profit or protect against loss, asset allocation helps manage the level and type of risks you face as an investor.

Finding the right balance between risk and return is key. Ideally, you want an overall investment mix that minimizes the risks you take while still aiming for a target return. For example, if you are seeking a 7.5% return, you might consider a portfolio split equally between stocks, which historically have averaged about a 10% annual return, and bonds, which have averaged around 5%. This example is purely hypothetical and not a guarantee of future results, but it illustrates how asset allocation can provide a starting point for building a portfolio.

Many financial publications offer model investment portfolios based on age or other demographic factors, which can serve as useful guidelines. However, these models are based on averages and may not fully reflect your unique financial situation, goals, and risk tolerance. Even individuals of the same age and income can have very different financial needs. Your asset allocation should be customized to your personal circumstances.

Diversification can go beyond just stocks, bonds, and cash. Other asset classes, such as real estate and alternative investments like hedge funds, private equity, precious metals, or collectibles, can also play a role. These types of investments often move independently of the major asset classes and can provide additional balance and diversification.

Even within an asset class, careful allocation is important. For example, when investing in stocks, you might divide your money among large-cap companies, small-cap companies, and international firms. When investing in bonds, you might choose a mix of short-term and long-term maturities, or select between taxable and tax-free bonds depending on your personal tax situation and the type of account you are using.

Monitoring your portfolio is just as important as setting it up. Over time, market fluctuations can alter your asset allocation. A strong stock market, for instance, might increase the proportion of stocks in your portfolio beyond your intended target, while a downturn could cause you to fall short of your financial goals. It is important to have a plan for rebalancing your portfolio when these shifts occur. Your approach should reflect your investment personality, including your tolerance for risk and your long-term objectives.

Even if you are satisfied with your current asset allocation, life changes — such as a new job, retirement, or a change in financial goals — may require you to revisit your choices. Some investments themselves may also change over time, so it is wise to periodically review your portfolio and the reasons behind your initial selections to ensure everything remains aligned with your needs.