Do you know of any exercises to expand one's attention span?

My young cousin has a hard time keeping focus. His mind is everywhere but where it is suppose to be. His mom suspects ADD but I believe it is just a 7 year old boy who has a lot racing around in his head and who needs help learning to focus. I’m a lot like him in that regard and it has caused me quite some grief in life. I want to help him avoid that. Does anyone know of a way to train your attention span? Any exercises or tricks?

I would be grateful for any suggestions. (Heck, I could probably use them myself) Thanks in advance for any help!