Regular overhand, throw strikes, especially in practice. In games, though, we tended to cheat just a little towards the hitters tendencies.
I prefer human pitch over machine pitch. Seeing the arm motion and delivery is important for developing hitters.
In the PONY "Pinto" division that we played in for ages 7-8, coach pitchers can't communicate with the hitter and have to exit the field of play on the certain side, etc.
It is neat that the coach pitcher is more like a team member than a coach.