Generally it should be facing down into venturi.  Some spray bars have two holes, in which case they should be front and rear, if the holes are off center they should be biased down into the venturi.  It's also been suggested that fuel draw is better with the hole positioned somewhere between straight down and horizontal to the venturi.  As long as it's not pointing up and out the venturi the engine will probably run. 

Above is correct.  However the ST spraybar in my Fox 35 got a little loose and rotated so the hole was looking at me.  Engine still ran fine.  Stupid Fox 35!