in addition to the above advice,
-disable the broadcast feature so ur neighbors don't know/can't detect ur wireless network. u know the name of ur network, no need to broadcast it to others!
-put in a static IP address, so u don't have to wait for DHCP to give u 1.
-move your router & modem into a basement, if you have 1. this will allow them to run a LOT COOLER, resulting in much greater reliability & less signal drops.
-when u lose connectivity, browse into the router (thru a connected PC) to see if it has internet access. if it does then the wireless portion has gone down (u need to reset router). if no internet, then the problem is upstream (cable modem).