Get your self XirrusWiFiInspector, install it on a laptop, then see what are the most common used channels in your area that are used by other WiFi routers.
Try Channel 4, it seems to work very well for me.
On a laptops WiFi card, disabled energy saving option. Google it how to change the option.
On a router, tilt the right antenna at 45degree angle to the right, and keep the rest of them straight up.
Read the sticky how to obtain 300mbps connection, you wont get 300mbps, but it has basic advice and guidance to help you with your issues.