7. Rely on your smartphone
For credit data harvesters, public Wi-Fi is an all-you-can-eat buffet. Ditto for those public-use computers in internet cafes and hotel business centers. Avoid them for anything other than reading the morning paper or checking the weather.
Need to check balances? Use your own cellphone to try your bank or issuer's app or mobile site, says Feddis.
Or go old-school and dial the institution's toll-free number.
In an emergency situation, if it's your only option, sometimes the benefits of Wi-Fi or public computers outweigh the risks, says Ridout, of Consumer Action. But usually there are better alternatives, and it's "generally a bad idea," he says.
And never put card numbers into websites that don't have a secure connection, says Velasquez. "My rule is that I use my (own computer's) secure network for sensitive transactions -- and would only use my phone if there was an urgent need and I was certain that the transmission was secure," she says.
Bonus security tip: Not using your phone that contains all of your banking and shopping info? Lock it. According to a study by Aite Group and ACI Worldwide, 11 percent of Americans don't.
"It's time we starting treating our phones like the computers they really are," says Velasquez.