Something I do on my Linksys wireless router. I have set static IP's for all of my computers that connect to the internet. Then I fleter all other IP's. The IP's are not the default 192.168.1.x series that comes up automatically for Linksys routers. I've blocked all MAC addresses except for my wireless cards on the router. I changed the SSID from the default, and don't broadcast it.
Basically, change everything from default to something that you know how to set, and you should be good to go.
Worked4me, even if you tell the router to not broadcast the SSID, it's usually fairly easy to tell the wireless adapter in your computer to look for that specific SSID.