A few years back, a fellow named Wylie Tollette faced some uncomfortable questions as he sat before the public oversight committee of the California Public Employees Retirement System (“CalPERS”). As the pension fund’s Chief Operating Investment Officer, Tollette was responsible for updating the committee on the status of its massive $350 billion portfolio. But, when a committee member asked about the fees CalPERS was paying to a particular group of investment managers, Tollette did not have a ready answer. “It’s not explicitly disclosed or account for,” he said. “We can’t track it.” In other words, CalPERS, the largest pension fund in the United States, was being kept in the dark by its own vendors — the funds it had hired to help manage its assets.

In his defense, Tollette noted that CalPERS was not alone in its inability to know what it was paying. “It’s an industry challenge,” he said. And, I agree with him. At the same time, though, when you are trying to build wealth, it is critically important to understand and to manage the fees that you are paying. According to multiple studies by the research firm Morningstar, fees are “the most proven predictor of future fund returns.” With that in mind, below are steps you can take to audit the cost of the investments that you own or that you are considering owning:

For mutual funds, the first number to check is what is known as the “expense ratio.” That represents the percentage of a fund that investment managers deduct to compensate themselves. For mutual funds holding domestic stocks, look for an expense ratio under 0.10% (that is, one-tenth of one percent). For a fund holding international stocks, expect to pay more, but no more than 0.15%. If a fund is charging much more than that, you really want to be skeptical. You can look up a fund’s expense ratio on the fund company’s own website or at Morningstar.com.

Mutual funds may also carry two other kinds of fees, both of which are cloaked in jargon and difficult to see: The first is called a “12b-1” or “marketing” fee. This is a fee that the fund company may pay to the advisor who sells you one of their funds. What makes these fees particularly distasteful, however, is that they are not simply one-time commissions; they are subtracted from your investment every year. The other type of fee to watch out for is called a “load.” This is similar to a 12b-1, except that it is a one-time payment. Unfortunately, however, loads can be sizable, eating up as much as five percent of your investment before you even get started. I would unequivocally advise against any fund carrying either of these fees.

Another statistic to pay attention to is something called “turnover.” What this represents it the percentage of your portfolio that is bought and sold each year. Whether you are looking at a mutual fund or at an advisor who manages a portfolio of stocks for you, turnover is important because it can have a serious impact on your tax return. If you look at a simple index fund like the Vanguard S&P 500 Fund, it will have turnover of just 4%. Look at many actively-managed funds, however, and many have turnover of 50 or 100 percent, or more. If you are unsure of the impact of turnover on your current investment portfolio, you can check your tax return or ask your accountant to help you.

If you are working with an advisor, here’s an another fee-related question to ask: Do they have any “soft dollar” arrangements with their brokers. Soft dollars are an opaque practice whereby an investment advisor tells a brokerage firm how much to charge its clients in trading commissions and then receives back from that broker a portion of those commissions. The investment advisor can then use those funds to help pay many of its own bills, within certain guidelines. The result is that you could end up — indirectly and invisibly — paying your advisor quite a bit more than you realize.

I know that what I am recommending here may sound like a lot of homework. So, if you wanted just one single strategy to help manage costs, what I always recommend is to opt for simplicity in your investment life. While certainly there are some complex investments that may pay off, in my opinion, I believe you put yourself in a much better position to succeed when you keep it simple.