Here’s a Watchdog Nation salute to three citizen watchdogs who set a fine example about how to be your own watchdog.

Meet Don Judd, a software engineer in Benbrook, Texas who never lets a worker into his house without seeing proof of insurance. He decided to make this his personal rule after a worker fell through his ceiling.

When DirecTV sent installers to his house without proof of insurance, he sent them away. Several times.

I contacted DirecTV, where a spokesman said, “This is the first time we’ve ever been asked for a certificate of insurance, and we obviously weren’t prepared to produce it.” He said the company has a new procedures to better handle these requests.

Tip: Remember to ask for proof of insurance and a contractor’s bond.

Meet Michael McGuire, a police officer, who got angry when the airbag system on his 2006 BMW wasn’t working properly. He researched it and found that there was a recall. But no dealer would fix his car because it missed the cutoff date for the recall by four months, even though it had the same problem. Cost of repair: $1,000.

He contacted me, and I suggested small claims court. He sued the manufacturer in Johnson County, Texas. But before his court date, he squeezed a final pressure point: He told the manufacturer he would file a complaint with the National Highway Traffic Safety Administration.

The company agreed to settle. McGuire withdrew his lawsuit. His car was fixed. For free.

Tip: The police officer hit the company with two pressure points. It worked.

And meet Matthew Howell of Arlington, Texas who wondered why his Sprint wireless bill increased $2. He called Sprint and a rep told him, “Well, our costs went up so we passed them on to you.”

He asked for a manager, who gave a different reason: He said the state and city had raised the sales tax. But that’s not true.

He wrote his state legislator, who passed his request on to the state comptroller’s office.

The office investigated and discovered that for one of the billing periods he questioned, Sprint had undercharged both state and local taxes. Luckily, the billing period after that, Sprint overcharged. But only by a penny.

The reason for the change in his bill? Something called the Federal Universal Service Fee Assessments, designed to make sure that all Americans have phone service. The program is administered by the Federal Communications Commission, and the rate changes every three months.

Many companies pass this fee on to their customers. So if the rate changes, the sales tax amount changes, too, by a few pennies or more.

Tip: Worth checking your bills because those pennies add up.

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Dave Lieber, The Watchdog columnist for The Fort Worth Star-Telegram, is the founder of Watchdog Nation. The new 2010 edition of his book, Dave Lieber’s Watchdog Nation: Bite Back When Businesses and Scammers Do You Wrong, is out. Revised and expanded, the book won two national book awards in 2009 for social change. Twitter @DaveLieber