The rules for 'turning' a missile are found in strat ops, my page is 100 but I have the old book. You take a small +1 penalty, but can 'torso twist' the missile from its firing arc as long as the twist happens in the first 1-3 hexes of movement, so its not quite as good as a torso twist (which is an arc change in hex 0, not 1-3).
EDIT: To turn a missile more then this 1 hex turn using 'capital missile waypoint launches', you need tele-operated missiles, which have lower velocity then normal missiles but can turn more.