I always:
-Disable SSID Broadcast, and
-Enable MAC Address filtering
Enter your macs Wifi address in the list, and select the option to only allow listed addresses on the network.
Your macs wifi address should be:
System Preferences>Network>Airport (click on "Configure") It is listed as "Airport ID" and looks something like 00:1d:45:t6:4e:40
edit:
remember to change the SSID from it's default name. give your network a new name. When attempting to connect to your network, Manually enter the name (SSID) exactly as you did on the router, then select Open (no security) and it should connect.