Quite simply I make sure the underneath side of the binding is placed a little higher than the front side, obviously this is hard to tell unless your using a sheer fabric, but on normal fabrics when you insert the pin on the right side (the side that will be seen) of the binding, it should come through on the wrong side with at least 2-3mm of where the binding will end. That way if there is any movement of the binging whilst sewing it should catch both sides of the binding with ease.
To help with this sewing tip you can also avoid ironing your binding exactly in half. Make sure the one side is folded a little less than half, this will then be your top side when pinning it to your neckline/arm hole.
Pins are first inserted around a 1mm from the bindings inner edge.
Where pins first come out from fabric there should be around 2-3mm from the inner edge.
Sew the top stitching close to the edge of binding for a professional look
And all of the binding should be caught on the wrong side too!!
This tip can also be used when stitching in the ditch, again make sure you insert your pin in the right side of the fabric that it catches the underside fabric with 2-3 mm to spare.
Hope that helps.