Layouts for countertops are a combination of all of the above. It is essential that the countertop layout be visually appealing. Full tiles should abut trim at the front of the deck. Full tiles should be at the bottom of the splash. Generally it is more visually appealing to have the trim and field centered on the sink. This is not always possible. It is necessary to carefully examine the top to determine the best layout. The layout will be dependent on the size of tile, joint width, and chosen trim/accents.
Tile Doctor Tip: For an in depth look go to Countertop Layout.