|paul is correct! For added security, you can also set up Wireless MAC filter, and Disable the broadcast of you SSID. Even Using Manual Assigned IP address instead of DHCP and subnetting your network will give you more security|
MAC filter is a access list you have to set up in the router, using only the MAC address of the Wireless Hardware that you want to connect, this way no one else can obtain a connection wirelessly untill there MAC address is added to the list.
Disabling you SSID will require the end user to maunually type in the SSID to connect the first time.
Using manual IP's is a bit over the top if you only worried about a home network, but i would recommend in a small business enviroment. This would require the end user to input a IP, subnet mask, and default gateway.
Subnetting is useful if you want to only have so many usable IP address on a network so if you only need say 6 IP's total this includes the Router so 5 usable IP's for end devices you subnet would look like this 255.255.255.248 instead of the typical 255.255.255.0