A push is a ball that goes directly to the right because of the action of the club. This should not be mistaken for a slice. A slice is an action of the ball spinning clockwise. A slice normally begins to the target and arcs away to the right, (left for lefties). A push is an action of the swing and is normally in an in-to-out swing motion. The opposite of the push is the pull, which is an out-to-in swing motion.
The push is caused by the swing path of the club. In the down swing, the path of the club will travel in an in-to-out path. Normally this is caused by throwing your arms ahead of your shoulders, being too close to the ball, and trying to over compensate your swing to make contact with the ball, or having your hips ahead of the impact area. These are the easiest to identify, but there could be other reasons.
The easiest way to fix a push is to go back to the basics of the golf swing. The push is directly related to the action of the golf swing. Throwing your arms ahead of your shoulders, make sure that during your back swing, you push your arms out with your shoulders, and on the down swing, you pull your arms down with your shoulders.
At the point of impact you should be back to the same point as you were at your stance. Standing too close to the ball, check out your stance. The club face should be positioned center of the ball and the butt end of the club should be about 4-5 inches from the inside of the left thigh and in line with it.
Having your hips ahead of the impact area, again, you should remember to be exactly the same at the point of impact as you were at your stance. The push comes from an improper club swing and knowing the basics.