When you use a public wi-fi hotspot, you need to realize that most of the data you are sending is going in “cleartext”. This means there’s the potential for a hacker to grab some personal data, such as passwords, email messages, session keys (for websites you’ve logged into), etc. With so many applications using the internet for communications these days, even if you are careful about using “https:” when checking email, or browsing, data can leak out.
One solution is to install a VPN on your computer. This encrypts all data on your connection, and will prevent any theft. One such VPN is http://openvpn.net/, (OpenVPN) which is free to use.
Once you set it up, all you need to do is connect to it after you get on the WI-FI hotspot network. Then you do all your normal web activities as usual.