For Belkin routers:
1) Enter your router’s config page by typing the IP address into your browser. This is 192.168.2.1
2) In the Wireless section, go to Settings and SSID. Change the SSID to something reasonably unique, like “My Wifi Network”. This achieves two things; it stops anyone from identifying your brand of router and it makes your network more obvious to you among those of your neighbours.
You can turn off SSID broadcast if you wish, but this sometimes causes pick-up problems with some devices.
3) This is the biggy; click on Security. From the drop-down, select WPA with Pre-shared Key (WPA-PSK). Now you need to pick a key, and it had better be good; a long mix of upper and lower-case letters, numbers and symbols, such as ydfPH9456#45=?ekny5834cbr. Make up your own and write it down for use later. When you are ready to connect a wireless PC for the first time, you will be asked for this key. It will be stored from then on, but keep a note of it anyway.
4) This is a bit more complex; click on MAC address filtering. Now, on each PC that uses your network, go to Start, Run and type in “command” without the quotes. In the box that has appeared, type “ipconfig /all” - without quotes, but with the space. Look for the MAC address and make a note of it. Once you have the MAC address of every PC, go back to your router’s config page and select “allow” from the drop-down. Now enter those MAC addresses by clicking on New MAC Address. If you later want to allow more devices onto your network, follow this procedure again.
5) Under the Firewall section, select Policy. It should already be set to typical. If so, leave it that way; if not, select it.
6) Go to Utilities and select Remote Management. If ANY of these boxes are ticked, untick them. By default, they will not be ticked.
7) In Utilities, select System Settings. This is where you set a password for the router’s config page. I cannot emphasise just how essential this is!! Enter a password that will be impossible to guess and tricky to crack with a password generator; it does not need to be as sophisticated as your WPA key, as you’ll need to type this password occasionally. Again, make a note of it.
And that's it.
(Copyright of ade.h!)