If you're the PG talk to him directly about the problem, if he's a cool person he'll respect that and try to better the situation. If you're a wing or big man run to the ball hog and demand the ball and let it be known to everyone watching that u want the ball. If he doesn't pass the coach himself will make note of this and step to the player himself. I know this because I was a ball hogging PG in 6th-7th grade and I changed due to good coaching. In high school I witnessed a ball hoggin wing player and I let it be known that I was running the team everytime he tried to get the ball on the inbound. Once I even stole the ball from him during practice lol. It was cool though he eventually gave in to the team concept, it takes time though.