Since Rowuk isn't here yet, I'll post my views.
I use a 1/3 top, 2/3 bottom approach. I believe this is probably the best approach for most people, however, lots of great players have used other placements. This is something that really comes naturally for most musicians. If I were you, unless you have serious issues in your playing that cannot be resolved with more practice, I wouldn't think much about mouthpiece placement.