Traditional sighting instruction recommends a sight picture that has front and rear sights aligned and the target sitting directly atop the front post much like a cat on a fence. This is also called a “Six O’Clock” Hold as the front sight is positioned at the 6 mark on a clock face.
Some, however, prefer to take a “Center Hold,” where the front post is held directly in the middle of the target.
When using open sights, concentrate your focus on the front sight, not on the target and not on the rear sight. With three separate items before your eyes, any illusion that you will be able to keep all three in sharp focus is exactly that, an illusion. The eye can hold sharp focus on only one thing. Make it the front sight.
A good sight picture will have the rear sight slightly fuzzy, the target slightly fuzzy and the front sight razor-edge sharp.