This is the guide I used, but there seems to be ample signage these days.

http://www.justvegasdeals.com/idiots...ransportation/

Regarding wifi, it's not dependable at all after you get out. I usually order it, wait until they're near, remember the license plate, then step out. For T3, just make sure you go down a floor after you cross the bridge, only confusing part.