If you want a pilots view then mount it in front of the windshield or on the center of the wing.
If you don't want to see the prop then go to the left or right on the wing. As mentioned keep it on the spar . Plus don't go too far to the end of the wing without adding equal weight in the same spot on the opposite side of the wing.

If the camera has a mount then secure that to the plane . If not then just mount the camera using some good quality velcro.