Security in wireless networks

I'm looking for ways to keep my computer secure in wireless networks, from the home AT&T U-verse wireless network as well as public wifi hotspots like the mall, the park, etc. My laptop is a HP Pavilion g7-1219wm notebook PC, with Windows 7.

I know the usual basic methods...setting the wifi connection to be automatically public, disabling remote connection and file sharing, putting a VPN on my computer, keeping my computer physically with me and not leaving it where others could tamper with it. I'm wondering about security from more sophisticated attacks though. Also, is there any way to keep private and secure whatever websites I go to in a wireless network, even from a network administrator? I know people have apparently been able to access that information both at home and in public wifi zones.

Do VPNs even work (especially the free versions), and if so, what is a good one that won't otherwise interfere with computer operation? I put Hotspot Shield on my computer for awhile, and it stopped me from being able to even connect to wifi. It also prevented me from getting to Google and instead kept routing me to its own search engine. It's still popping up even though I un-installed Hotspot Shield and its toolbar.

Thanks for any tips/tricks.