S-Bend Explained

Start with just 2 or 3 poles and accustom your equine to
walking over them a number of times, before forming your S-Bend.
Approach the S-Bend and allow your equine to take a good look at it.
Halt at the entrance and turn and face your equine.
There is no hurry.
You, the handler, are going to walk backwards facing your equine. 
Move with "soft" knees, ground yourself, you want calm slow energy.
Your body position should be upright, leaning slightly backwards, projecting your energy out towards your equine - this is to help slow him down.
You both need focus and attention to negotiate the bends.
Ask your equine gently, for his attention.
Use all the space available to make the turns.

Tip - to "warm up" for the S-Bend,

ask your equine quietly, to make small very tight turns, you want to see him using his inside hind leg, the leg nearest you, to step under himself. Moving the hind leg across and under his body, and in front of the other leg, and not shuffling from side to side.