Up til recently, for channel planning, I've simply been picking the channels with the lowest RSSI.
But this isn't a great method, as beacon channels at high RSSI may have way less collision than other channels with less RSSI.
What tools do others here use to easily analyze this sort of thing? (F/OSS ones are preferable)
The channels you should be using for 2.4GHz (assumed) are channels 1,6 and 11. If you have someone around you that is on an overlapping channel, well, that is a different procedure to take care of that. :)
Assuming that others are using 1, 6, or 11, you should set your AP's to the channels with the least amount of 802.11 traffic in that area. When speaking of 802.11 technologies only, it's all about channel usage. RF interference is another discussion...