In terms of general tips, Jeremy1026's is good. Find the least-used channel in your area and switch to it. If you can find a block of three consecutive low-traffic channels, that's even better: pick the one in the middle. Again going back to Jeremy1026, 4 is often a good choice in the US, and you can also try 8 or 9 if 4 doesn't work out. But if you've got a lot of savvy people in your area looking for a good channel, you may need to look deeper.
Many routers can perform something they usually call a "Wireless Site Survey" to help you find a relatively unused channel. At least in Linux, you can also use the iw family of commands, though there's a lot of output to sift through. I don't know what's out there for Windows in this regard, but there's got to be something.