On my 701, plug in the USB stick first. I press F2 to get into the "setup" screen (i.e the BIOS). There, use the arrow keys to go to the Boot tab. If you look under Hard Disk Drives, you should see the USB device listed - then you use the + and - keys to set the USB device as the first drive option. I don't think you need to enter the Boot Device Priority section. The F10 to save the settings and the laptop will reboot into your USB device.
Hopefully that should work - any problems repost and I will get my EeePC out and boot it from the USB key to double check.