You can easily list the channels currently used by other APs by running a free Wi-Fi discovery tool (aka “stumbler”). Since you’re using a PC, try MetaGeek InSSIDer or Xirrus Wi-Fi Inspector or the infamous NetStumber. But keep in mind that those other APs may be automatically changing their channels too, trying to find “cleaner” air.
It’s possible that you’re experiencing so much 2.4 GHz band congestion that you won’t be able to find a clean channel. Try sorting your neighboring AP list by signal strength and picking the channel (1, 6, 11) with fewest strong-signal neighbors. It doesn’t help to pick a channel in between these as that channel will overlap at least partly with 1, 6, or 11.
You may also be able to increase the signal strength of your own AP by making sure its dipole antennas are in parallel (usually vertical) positions and that the path between the AP and your client isn’t blocked by something especially dense like a brick wall or a source of 2.4 GHz RF interference like a microwave oven, Bluetooth peripheral, or 2.4 GHz cordless phone. If you’ve picked the cleanest channel, your laptop is sitting within a few feet of open space from your AP, and you still can’t maintain a strong connection, you’ve probably got a different kind of problem.