In the USA, the common channels are 1, 6, and 11. The router I set up last night defaulted to channel 6 but I've seen defaults to the others as well.
The best way to determine interference is to do a site survey and pick the least-used channel. This is what I do for customers. Sometimes all 3 have numerous other APs on them and interference and crappy reception can't be avoided. Such is life.
If your wifi spectrum is too crowded you should skip wifi altogether and go with the USB LAN adapter and run a network cable.