here is how i wired mine, this should clear things up for you:
really though, the wiring diagram linked is exactly how to do it. for mine i bought some romex, 2 male and 1 female plug, and some wire nuts. the wire to the wall from the balast i wired to a male plug, the wire to the light i wired with a female plug, and then the wire coming from the lamp i wired as a male plug. this allows me for fast disconnects. my lights use yellow plugs for the lamp to ballast connections, and orange plugs to lead to the wall.
for safety, i ran both of my 250 ballasts through a 15 amp gfci, which in turn plugs into a timer.
i am going to be cleaning up the wiring in the next couple days to prepare for this months club meeting, if you want some more photos i can take them for you.