its cycle from left to right, or right to left.
if you see 3 mobs on screen, pressing left to right, will target the right mob, and the opposite targets the left mob 1st. pressing again will cycle back around to the opposite, and then the middle one.
i forget which button, i think the accept button, lets u pick the nearest enemy you're facing. so i pick between those 3 options.

if too many mobs are on screen, i point the camera down, to limit the number i cycle between.