Key Points
As an umpire to make a fair or foul decision you should make every effort to get on the line to make the call.
Straddle the line and stop before the ball settles, is touched or first falls.
Remember that all bases and home plate are in FAIR territory. Any ball which strikes a base directly from a hit will be a FAIR BALL.
A ball resting on Home Plate will be a FAIR ball.
Before 1st or 3rd base it is where the BALL stops or is touched.
After 1st or 3rd base it is where the BALL lands or is touched.
What the Rule Book Says
FAIR TERRITORY is that part of the playing field within, and including the first base and third base lines, from home base to the bottom of the playing field fence and perpendicularly upwards.
All foul lines are in fair territory
FOUL TERRITORY is that part of the playing field outside the first and third base lines extended to the fence and perpendicularly upwards.
A FAIR BALL is a batted ball that settles on fair ground between home and first base, or between home and third base, or that is on or over fair territory when bounding to the outfield past first or third base, or that touches first, second or third base, or that first falls on fair territory on or beyond first base or third base, or that, while on or over fair territory touches the person of an umpire or player, or that while over fair territory, passes out of the playing field in flight.
A fair fly shall be judged according to the relative position of the ball and the foul line, including the foul pole, and not as to whether the fielder is on fair or foul territory at the time he touches the ball.
A FOUL BALL is a batted ball that settles on foul territory between home and first base, or between home and third base, or that bounds past first or third base on or over foul territory, or that first falls on foul territory beyond first or third base, or that, while on or over foul territory, touches the person of an umpire or player, or any object foreign to the natural ground.
A foul fly shall be judged according to the relative position of the ball and the foul line, including the foul pole, and not as to whether the infielder is on foul or fair territory at the time he touches the ball.