Before using a Free Wi-Fi in a a coffee shop, or library or wherever...ask the staff the name of the network to verify it. As Savvides points out -- it's easy from someone nearby to create a fake network called "Free Wi-Fi" -- or even one that says "Starbucks" in the name, and hijack your account when you log in.
Some of the suggestions are a bit convoluted, and more than most people will likely do. But one -- which takes a couple of steps -- is still very easy and a huge safety net. In Windows, go into your Control Panel and turn off "File Sharing." That way, if you are hijacked, your files can't be accessed. Then you turn it back on after you log off. (The article shows you how to easily do this, and what to do with an Apple device.)
You can read the whole article here.