A brand new leather basketball won't have the feel and grip for which leather balls are known. Newer balls made of composite materials don't have the need for a break-in -- they come ready to go right out of the package -- but leather balls do. The easiest way to break in a leather basketball is by playing with it on the court. However, you can speed up the process of breaking in a new leather ball.
Wipe down your leather basketball with the dry cloth to remove any loose dirt.
Spray half of the ball with the leather conditioner, and gently rub it into the ball using the damp cloth in a circular motion.
Allow the conditioner to dry; it will take about 15 minutes.
Wipe off the excess conditioner using a dry cloth, and repeat the process for the other half of the ball.
Repeat the entire process from the beginning two or three more times until the leather softens and loses its glossy, sleek factory feel.
Tips
If you want to break in your leather basketball without using leather conditioner, your best bet is to play with the ball regularly. It will take some time, but your ball is guaranteed to soften this way.