Also, apart from enabling encryption, you can turn off the SSID (network name) broadcast, reduce the number of available DHCP addresses, disable remote/wireless configuration of the router.
Activate the MAC filter, by noting the MAC address of your wireless adapter, typically, click start, run then type cmd.
At the prompt type "ipconfig /all" - without the quotes, look for the entry for your wireless adapter and look for physical address, enter this into the MAC filter and only this adapter will be allowed wireless access.