Washing your hands after using the bathroom — not to mention after touching any number of public surfaces, from doorknobs to subway handrails to oh-so-disgusting toilet flush levers — is a basic rule of hygiene. Yet we don’t always do it properly, if at all, which is particularly ill-advised behavior during flu season, when germy hands are common gateways to infection.

Respondents to a recent survey said they washed their hands an average of 87 percent of the time after using a public restroom, and 62 percent said they have rinsed their hands post-bathroom without using soap. The survey of more than 1,000 people in the U.S. was conducted by Bradley Corp., manufacturer of washroom accessories. Women are significantly better hand washers than men.

Those self-reported findings echo habits observed in an a 2010 study from the American Society for Microbiology and the American Cleaning Institute, a trade association for the soap and detergent industry, which sent observers into public restrooms to record people’s hand-washing habits. They saw 85 percent of people wash their hands, an improvement from 77 percent in 2007. In a survey that was part of that same study, 77 percent of respondents said they always clean their hands before handling or eating food. Only 39 percent said they always wash their hands after coughing or sneezing.

Considering that people absent-mindedly touch their faces an average of 16 times an hour, according to a 2008 study by researchers at the University of California at Berkeley School of Public Health, and risk transferring germs from their dirty hands to their eyes, noses and mouths, lazy hand washers could use a refresher.

“The big mistake people make is that they just rub their palms together and they don’t get to the dirtiest parts of the hands” — under and around the fingernails,” said Elaine Larson, associate dean for research at Columbia University School of Nursing. The key is to cover all surfaces of the hands, including between the fingers and in the crevices around fingernails, with a good amount of friction, Larson said. Using soap is important, not because it kills bacteria, but because it acts as an emulsifier to slip the germs off the hands, she said.

The Centers for Disease Control and Prevention says washing your hands should take about 20 seconds, or about two rounds of singing “Happy Birthday.” The temperature of the water doesn’t matter. It’s best to dry your hands with a paper towel so you don’t just rub them on your dirty pants, but better to let them air dry than use a shared towel, Larson said.

Hand sanitizers are a convenient alternative to hand-washing. Pick one that is at least 60 percent alcohol, and use enough so that your hands are wet for 10 seconds so it has enough time to kill the bacteria, Larson said. Alcohol sanitizers only work when they’re wet, she said.