The hard core geeks know that to optimize your wireless networking experience you want to select a channel that is unused by other nearby wireless devices.
If you run Windows 7 (or Vista), use the following command at the Command Prompt to see the channels and signal strength of nearby networks:
netsh wlan show networks mode=bssid
The channel numbers will be in the range of 1 to 11. Find a hole, ideally at least five channels away from your neighbours, and change your wireless router configuration to use that channel. If you are in an area with lots of wireless networks, focus on avoiding interference with the strongest competing signals.
Slightly Deeper Explanation
Your 2.4 GHz wireless device does not actually use the exact frequency of 2400 MHz. If your wireless networking device is configured to use channel 1, it is operating using the frequency 2412 MHz. If your wireless networking device is configured to use channel 6, it is operating using the frequency 2437 MHz.
Radio frequency communication is not as neat and tidy as those single frequency numbers imply. Your wireless router actually operates over a frequency range or spread. Channels are 5 MHz apart but the frequency spread of each channel is 25 MHz (12.5 MHz above and below the channel’s center frequency). That means you have to move 5 channels (5 x 5 MHz) to completely avoid interference between channels.