As with other wands, it spends charges with each use, and can be used continuously .
It does 5 damage per hit. If you fire the wand continuously, It will not appear to miss, but it may do no damage.
It only works if you are aiming at a mob. if you shoot an empty space or a location ouside of the wand's range, it does nothing.
It is possible to fire the wand through solid walls, damaging mobs on the other side. This can help you get rid of spiders camping out on your roof.
A good use of the Wand of Lightning is to kill Ghasts. However, a Ghast may often be able to fire at you from beyond your wand's range, so it's still best to have a bow with you as well when you travel to the Nether.
See also: Thaumic Restorer