The key to Warren Buffett's empire doesn't lie solely in buying great businesses at good prices. Instead, Berkshire Hathaway (NYSE: BRK-A) (NYSE: BRK-B)'s success stands upon a rock-solid foundation of trust.

When Buffett and his partner Charlie Munger buy businesses, they want to deal with people on whom they can rely. From See's Candy to Dairy Queen to NetJets, Buffett and Munger have often noted how much faith they place in the managers of Berkshire's many properties. This trust frees manages to be responsible for their own divisions, without worrying about micromanagement from above -- and liberates Buffett and Munger to spend more time picking great investments, and less time nitpicking their subsidiaries.

I suspect that in most cases, their trust also inspires the Berkshire companies' leaders to deserve that confidence, and to deliver in spades for Buffett. Over roughly 40 years, Berkshire Hathaway's book value has grown at an annual rate of more than 20%.

Investments you can rely on
Trust is a double-edged sword. It can inspire hard-working managers and loyal customers when gained -- or threaten to destroy a business when lost. For decades, Japanese cars were considered more reliable than American cars, even as U.S. automakers improved their product quality. Now, as Toyota (NYSE: TM) faces the biggest threat to its reputation in its history, import-wary consumers have given Ford (NYSE: F) and other U.S. automakers an opportunity to regain their lost market share.

As you seek great investments for your portfolio, well-trusted companies provide an excellent place to start. Forbes magazine recently worked with the folks at Audit Integrity to find the 100 "most trustworthy" companies that "have consistently demonstrated transparent and conservative accounting practices and solid corporate governance and management."

I've singled out a few trusty picks from Forbes' list, along with additional factors that make them appealing investments.

  • Fluor (NYSE: FLR) is an engineering company primed to profit as our global economy rights itself. It's a key player in infrastructure, and has won several lucrative contracts in recent months, especially in Australia's mining industry. More importantly, the company enjoys a sterling reputation as one of the safest companies in its industry.
  • Lowe's (NYSE: LOW) is another cyclical company, likely to get a big boost from an economic turnaround. Its 1.5% dividend yield might not be the most attractive right now, but the company has hiked its dividend aggressively in recent years.
  • Under Armour (NYSE: UA) is a growth machine with a strong brand in performance apparel. It's likely to build on its strong growth record as it ramps up its expansion in the performance shoe segment.

Put trust to work
If you make your own buy and sell decisions with stocks, you should trust yourself, too. Buying without conviction is little better than gambling. Ask yourself whether your money is invested in your best ideas. See if you can fill half a sheet of paper or 30 seconds with reasons why you own a stock.

The more you believe in your holdings as great companies that will dominate their competitors, the more your portfolio's performance will likely resemble that of Warren Buffett's.

Longtime Fool contributor Selena Maranjian owns shares of Berkshire Hathaway. Berkshire Hathaway and Lowe's are Motley Fool Inside Value choices. Berkshire Hathaway and Ford Motor are Motley Fool Stock Advisor recommendations. Under Armour is a Motley Fool Hidden Gems pick and a Motley Fool Rule Breakers selection. The Fool owns shares of Berkshire Hathaway and Under Armour. Try any of our investing newsletter services free for 30 days. The Motley Fool is Fools writing for Fools.