This is how I made a usb cantenna with a coffee can. Simple and effective enough to gain 1 or 2 bars. Sorry bout the cr@ppy pics.
Step 1: Materials & Tools
11.5oz coffee can
Usb Wifi Adapter w/ or w/o usb cradle
Razor knife to cut can with. I'm not blessed with a dremel. :(
Needle nose pliers and/or wire cutters
Duct tape because it has a light and a dark side