There are several things you can tray to get better range with your wireless router.
1- Place it on the wall or on a selve in a high area.
2- If it has an external antenna make sure it is properly connected and not covered by any object.
3- If you have a N capable router, choose to transmit only with N (make sure all your devices are N compatible)
4- If your router has detachable antennas, you can get a directional antenna.