Finding the best wireless channel in OS X
If you've found yourself wanting to know what the best wireless channels in your area are, and you have a Mac available, you're in luck! OS X ships with a GUI application that can help you out.
Wireless Diagnostics can tell you which channels are currently being used, and give you a recommendation as to the best one available.
You can launch Wireless Diagnostics through spotlight, or by
Alt+Clicking the wireless icon in your toolbar, and clicking
Open Wireless Diagnostics....
Once Wireless Diagnostics opens, you'll see an introduction screen offering to scan your network for problems, but you can just ignore this window (but leave it open, or the app will stop running).
Next, go to the menubar and choose
Window > Scan.
This will bring up the Scan window, where you can see a full list of the networks in your area, and additional details about each network. You can click
Scan Now anytime to refresh your results.
The Scan window will also have a panel on the left that displays which wireless channels it thinks are the best available options, for both 2.4GHz and 5GHz.
As in most cases, the term "best" is just an approximation. Wireless channels are complicated, and just because one channel is open doesn't mean it's automatically the best choice. Since wireless channels are actually ranges of frequencies and they overlap with each other, neighboring channels can interfere with each other even though they are separate. There are some very interesting threads on Super User about the subject, if you're curious.