A nasty slice off the tee is the Achilles' heel of many amateur players' golf games. An inside-out golf shot occurs when the club is brought back "inside," or close to the body, and swung down from "outside" the ideal plane, away from the body. This swing causes the ball to spin perpendicular to the target line, leading to a ball that bends sharply off target in mid-air.
Stand over the ball squarely before swinging the club. In a square stance, the feet, hips and shoulders all point down a line parallel to the desired target line. A slice is commonly caused by a player that is leaving one of these components "open," meaning that the lead shoulder, foot or hip is farther back from the ball than the rear shoulder, foot or hip.
Check your grip, and consider strengthening the grip if it is weak or even neutral. Grip strength refers to the relative position of the thumb of the bottom hand to the top hand. When the two align, a grip is neutral, while a grip becomes stronger as the bottom hand turns forward or weaker as it turns back. Slices can be caused by a grip that is too weak.
Move the ball slightly forward in your stance. A slice can be a sign that you are hitting the ball before your club is completing its downward arc, which can cause an open club face and produce the slicing effect.
Stand more erect over the ball. Being too hunched can lead to the club swinging in a flatter arc, which is more likely to create a greater deal of spin perpendicular to the ball's flight path.
Relax over the ball, both physically and mentally. Tense muscles will prevent the club from releasing properly, while overthinking shots and obsessing over the potential bad results often yields its own bad shots as the player fails to let his natural muscle memory control the swing.
Keep your eye on the ball throughout the swing. Lifting the head, and losing sight of the ball, can often lead to errors in the swing path, which can lead to a slice.