If the batter is hugging the plate - inside pitch. If the batter is back from the plate - outside pitch.
This is the most obvious and basic one to give her.
For a bunt, a high fastball, or better yet, a rise ball, makes them pop up or foul. A pitch around the knees seems easier to bunt properly.
This is another one to remember. I haven't had a safe bunt put on me in two years.
In regards to bunt situation. First ball high (or rise if they can do it) The next ball should then be low inside. It jams the batter up as they expect you to throw it high again.