If you're operating a Wireless LAN (WLAN) you should be at least using WEP (Wired Equivalent Privacy) to encrypt your data, because anyone on the street could be eavesdropping you while you are sending passwords or pins. Note that WEP cannot offer much security (see this page) but I encourage you to use it, because it keeps script kiddies and other people who stumble over your net by accident, outside.
On Access Points that have the feature you should also enable WPA (WPA2 if available).
It's also wise to disable "broadcast SSID" - nobody needs to know your accesspoint's name except you!
And last but not least you should enable MAC adress filtering.
To ease the creation of WEP Keys I wrote a small utility that randomly creates hexadecimal keys which you can use for your home net.
Download it here [~250Kb]