Okay, first things, is it a USB 1.1 or a USB 2 device that you want to
extend? If it's a USB 2 device then make sure that you don't mind it
dropping down to being USB 1.1 performance as USB 2 only has very
severe drop off range.

Second, make darn sure that you split the other end of the cable before
it plugs into your router/switch/hub/modem/etc other wise you may blow
the poor thing up.

Third, be prepared for the performance of the network cable to drop
down to about 25mbps due to the ammount of interference on the line
(packet collisions, dropped packets, retransmissions etc).

Other than that it's fairly basic wiring. The USB bus is a 4/5 wire bus
with the fifth wire commonly used as earth, this nearly always the
outer shell of the USB connector. Just make sure that the pins all
correspond and your away. No technical challenges what so ever.

Hope this helps a little.

Seri