You see, putting a spell on someone across the world, is no different for them to be right next to you. Think of it as, all souls are packed together, with no distance.
When doing this you will feel, and if your a Psychic, see them, closer, you might get to feel their energy, That is reserved for people who have been into this stuff for 80+ years.
There is no distance, you want to put it on there soul. This will generally make it more effective, the spell, and cause things to be seen quicker, results.
This is reason of: The soul is the very being of a person, once attacked they can buckle, so do not make the spell TOO strong.