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Christine Benz is director of personal finance with Morningstar US.

"Nobody wants to be stupid. You know, once you're in the room with the Treasury Secretary or the CEO of a Wall Street firm or even just some hot-shot Wall Street trader, you don't want to seem like the idiot journalist who doesn't know what this is or why this works, because the natural response from the authorities is to ridicule you.

But the obvious questions are usually really the best questions. So, like, the obvious question now? All right, Hank Paulson, treasury secretary, you just gave US$200 billion to banks to make loans, banks that have proven they were bad at making loans because they would be bankrupt without you giving them money. Why give them the money?"

Michael Lewis, author of The Big Short and Liar's Poker, on NPR's "On the Media," 21 November 2008.

Lewis' point is an important one, and not just for journalists. Rather, his advice is sound for any consumer navigating the financial marketplace. Before you buy that quadruple-inverse Treasury exchange-traded fund, add a futures-based hard-assets investment, or pull the trigger on a large purchase like an annuity, make sure you ask the big, obvious questions first - of yourself or whoever is recommending the investment to you.

And until you've exhausted all of your so-called dumb questions and understand in an excruciating level of detail the mechanics and the specifics of what you'll pay and what could go wrong, feel free to pass on that investment.

After all, the aim of any industry is to get people to buy stuff and spend money. Some of that stuff is terribly helpful - think antibiotics and irons that turn themselves off - and some of it, not so much. (Looking at you, electric martini shaker.)

The same holds true for products coming out of the financial services industry, though I'd argue that the useful/usefulness ratio for financial products is even lower than is the case for other industries. In contrast to cars that we drive, clothes that we wear, or stuff that we use around our houses, most of us don't have hands-on experience with financial products, so we're not in a position to size up which financial products are likely to work well for us and which aren't. In turn, we might not even feel knowledgeable enough to ask the questions we need to make informed decisions.

So what are the best "dumb" questions to ask to ensure that you don't get talked into - or talk yourself into - a product that's useless or even harmful?

Here's a short list.

How does it work?

I'm not saying that you need to be able to get a job on a bond-trading desk to buy a fund that invests in inflation-linked bonds. But you should have a working understanding of the basic features of inflation-linked bonds and their mechanics. You should know, for example, that your return will consist of a basic interest rate as well as an inflation adjustment, that the securities carry little credit risk but tend to be interest-rate-sensitive, and so on.

Morningstar.com.au includes reams of data about the performance and portfolio characteristics of individual investments, but before you find yourself venturing too far into the weeds, make sure you understand the basic premise and mechanics of an investment type first. And if you don't have the financial background to get your arms around how an investment works, you're much better off steering clear.