When you put two pieces of drywall head to head, like on the ceiling, there is no tapered valley to hide the paper and drywall compound. The secrete to hiding this joint, which will be raised above the surface, is to spread it out as much as two to three feet wide.
On this TV show we visited an old pro, Gino Debono. He makes his final pass with a three feet wide piece of steel stud floor track -- a real inexpensive but very wide trowel.