One of the other considerations with wifi is that you have 13 channels to play with (b/g/n, not a), and each channel overlaps 2 others either side of it to a lesser extent. Hence, to get the best range and throughput, audit your airspace for all the broadcasting access points, their strength and the channel they're using. If you can sit 4 channels away from everyone else you're laughing, but if not then configure your access point's channel as far away from the crowd of other access point channels as possible.
e.g. if you had 4 APs you would configure them to channels 1,5,9, and 13. However if your neighbour has an AP on channel 6 (because we suffer from the yanks thinking we don't get channel 13 and hence configuring 1,6,11 as defaults into their kit) then you would want to site your APs on channels not including 4-8.
This diagram explains it even more elegantly:
List of WLAN channels - Wikipedia, the free encyclopedia