Industry standards are to lower the needle to DBC (dead bottom center, aka it's lowest point). The raise the needle .092". The point of the hook should now be in the middle of the scarf, the cut out on the side of the needle opposite the long groove. On household needles that is the side with the flat. If it isn't then the hook needs to be rotated until it is. To rotate the hook, one usually needs to loosen set screws on the hook shaft, and then rotate the hook by hand.
Some machines need to have the hook tip very slightly before the scarf and some more into the scarf.
On Singer machines with the timing marks the .092" is when the bottom timing mark is just at the lower end of the needlebar bushing. Knowing that helps to set a needlebar that has been previously moved.
Cathy