I agree with brighteyes... sidepassing is something taught after both fore and hind quarters can be moved individually on the ground, and undersaddle without issue... normally you will cue the forehand at the cinch, the hind end near the rear cinch, and for the entire body (side passing, in this instance), in the middle of those. When the horse is in an advanced stage of learning, you won't notice the rider's cues, because they are so close together, but when the horse is learning, don't be afraid to space out the cues to really show the horse what you want.
On the note of removing pressure, I don't do so until I get atleast one step in the direction I am asking, and then I remove all pressure, so the horse knows that is exactly what I wanted. I start on the fence, as well.
"The ideal horseman has the courage of a lion, the patience of a saint, and the hands of a woman..."