Great news: We're eating less bad stuff! The results of a recent study by the U.S. Department of Agriculture found that Americans say they're consuming fewer calories and cutting back on fast food, cholesterol, and fat. Furthermore, working-age adults consumed 118 fewer calories a day in the 2009-10 period than in the 2005-06 period, with more Americans eating home-cooked food as opposed to eating out in restaurants.

Of course, the credit crunch may be partly behind the study's findings, with more Americans turning to cheaper, home-cooked alternatives to restaurant food. Moreover, the study and the possible effects of the credit crunch on calorie intake got me thinking: Would a similar study indicate that Americans are investing better as a result of the credit crunch? Are they researching the companies they invest in to a greater degree? Or are the dark days of 2009 now forgotten in the American psyche, after years of Federal Reserve asset purchases have inflated asset prices to wonderfully high levels?

Eating less fat, salt, and sugar and instead eating more fruit and vegetables are simple things that all Americans can do to become healthier. However, if Americans were to try to "invest better," which three things could they do -- or not do -- to achieve that aim?

Here are three things I think we all could do to invest better -- and don't forget to let me know your ideas in the comments box below.

1. Focus on debt levels
With the Fed announcing the beginning of tapering of its monthly asset-repurchase program, it appears as though we are on the road, albeit a long one, to rising interest rates. Although it may take some time for them to go up, interest rates should be on the radar for all Foolish investors, with highly indebted companies having the potential to suffer the most from such increases. Sticking to companies with low to moderate financial gearing could be one solution.

2. Pay attention to relative valuations
The wider stock market was significantly re-rated upward in 2013, so stocks that still trade at a discount to their sector and to the market (for example, having a lower price-to-earnings ratio) have the potential to be re-rated upward so as to put them in line with the wider market. Although quality usually costs more, it may not cost as much as you think and could provide relative outperformance in future years.

3. Keep an eye on growth
In the aftermath of the credit crunch, the focus was on high-yielding, defensive stocks. This was understandable, since interest rates and bond yields were at record lows, so many investors needed an income, and companies with generous yields were the obvious solution. However, the focus has shifted to growth, and companies that offer above-average profit growth are in demand. While a growing economy should be good for all companies -- a rising tide lifts all boats, after all -- higher-growth, cyclical companies should benefit the most. Companies that can't offer high-single-digit earnings-per-share growth per annum may prove to be unpopular.

Of course, this it not an exhaustive list, and suffice it to say that Fools should look at more aspects to a company before they decide whether to invest. However, by focusing on at least these three areas in the coming years, Americans could be wealthier as well as healthier.

What would you suggest to help Americans invest better?