Netstumbler can be a good quick tool to see what APs and channels are in use. But for the love of god ignore the rest of his advice. In the 2.4GHz band only use channels 1, 6, or 11. If your neighbors are on 1 and 6 strong, but a weak neighbor is on 11, then you use 11. If you go to channel 9 as he suggests you will get interference from both channels 6 and 11. Same holds true if you pick something between 1 and 6, then you will get interference from those two channels.
(Massive edit from my original reply follows)
What I've learned today: this
is an oversimplificationthis
seems to be more true to life.
The difference between 20MHz and 22MHz per channel, is the difference between
Same holds true if you pick something between 1 and 6, then you will get interference from those two channels
being true, and not being true. Because it appears that wi-fi channels are actually 22MHz, not 20MHz as guesstimated on dslreports, my original reply here no longer makes any sense. By the DSL reports metric, channel 10 would only overlap 11, and not 6. In the real world, unfortunately, there is a reason why my first recommendation (and the commonly portrayed standard) is to only use channels 1, 6, and 11. I used the 3, 4, 8, 9 scenario in the past, and apparently I got lucky.