A rule of thumb is a useful principle of a broad application not intended to be strictly accurate or reliable in every situation.

A rule of thumb is a useful principle of a broad application not intended to be strictly accurate or reliable in every situation.

Virtually every profession or business endeavor has established rules of thumb. Parents and teachers employ such rules to guide behavior. Growing up, when I went somewhere, my mother provided this rule of thumb, "Don't be naughty!" Later, she offered this guide for making a speech: "A speech should be like a lady's dress, not too long, not too short, but cover the important parts."

Rules of thumb have been around for a long time. Many were popularized in Poor Richard's Almanac:

• A penny saved is a penny earned;
• An apple a day keeps the doctor away;
• Early to bed and early to rise makes a man healthy, wealthy and wise;
• People who live in glass houses shouldn't throw stones;
• Don't put all your eggs in one basket, and;
• A stitch in time saves nine.

You know that a picture is worth 1,000 words and that your freedom ends where my nose begins. Youngsters taking their driving test should remember to maintain at least one car length for every 10 miles an hour of speed. As a school administrator, one of my rules of thumb was to never spend non-recurring revenue for recurring expenses. Public officials learn not to argue with those who buy ink by the barrel. As per Rush Limaugh, to sell the big lie, "Salt it with a little truth." Hillary Clinton reminded us that it takes a village to raise a child. The old classic rule of thumb is all it takes for evil to triumph is for good people to do nothing. And the greatest of all is, "Do unto others as you would have them do unto you."

Ridiculed for his long legs in the Lincoln-Douglas debates of 1858, Lincoln reasoned that a man's legs should be long enough to reach from his body to the ground. Louise Hendrix was one of the six graduates in the first class at Neosho High School in 1889. For the next 46 years, she was a teacher in the Neosho school system. I once asked the late Raymond Welcher what he remembered about her. "Plan your work, work your plan," was his response. Wet or dry, plant your turnips on the fourth of July. Is this really a rule of thumb or am I mixed up?
All rules of thumb are not universally accepted. An English judge of the 1770s has been lambasted for allegedly ruling that it was legal for a man to beat his wife if the stick was no thicker than your thumb. Years ago, I labored under the assumption that a family could afford to spend 2 ½ times their annual salary to buy a house.

Wholesale violations of a much more liberal rule contributed greatly to the banking-housing meltdown.

Even the military has its rules of thumb. Perhaps the most popular one is "Never volunteer for anything." I still enjoy using the flash-bang rule of thumb for estimating distance. When you see the flash of a weapon firing, begin counting at the rate of 17 per five seconds until you hear the bang. This will approximate the distance to the weapon in hundreds of yards. The same technique can be used in determining the distance to lightning or fireworks. When you see the flash of lightning or the blast of fireworks, begin counting at the speed noted above until you hear the thunder or the report of the fireworks. This will reveal with amazing accuracy the distance to the lighting or fireworks. Check it out over the Fourth of July holiday.

Poet Maya Angelou's observation would serve as an excellent rule of thumb for dealing with people: "They will forget what you said; forget what you did; but they will never forget how you make them feel."

Roy Shaver writes a weekly column for the Daily News.