Real King Air pilots suggested to me that the trim should be set just below the "up" on the trim wheel for take-off, which I find works really well!   For cruise, or level flight shall we say, its normally close to the 0 (thats what ive noticed with my autopilot on anyways), and for landing, it usually ends up close to the up again, but really depends on how you like to land your plane, you just adjust it up and down until you feel comfortable.