During the crossover, your son should learn most of the information needed to get the Scout badge when he gets to a troop- Scout Slogan, Motto, Oath and Law. If he crosses over with a group of boys, they might form their own patrol or it might be good to get with an existing patrol- some older Scouts to act as leaders.
Troops are generally run on the patrol method and youth leadership is the guide. The Senior Patrol leader (older boy) in general runs the troop with supervision and guidance from the Scoutmaster. Boys plan their trips and activities. Your son's patrol will do things together and will compete with other patrols in activities and events.
Unlike Cub Scouts, parents can not sign off on requirements (most of the time). Review requirements with your son and guide him along the trail. Initially he will be getting used to his new troop. Things will be strange for him and he will be trying to find how to fit in. Stay with him and encourage him. What bonds these kids is shared experiences. After his first campout, things will improve, he will have stories to share and events to discuss.
Summer camp will be another bonding activity. I know it's a long way off, but his first summer camp is an excellent advancement opportunity. Most camps have a program that focuses on Tenderfoot, Second Class and First class requirements. He will also have time to work on merit badges. Let him take the badges he wants but have him take at least one Eagle required merit badge- I usually suggest Swimming (it's hard to get away from camp).
Hope that helps. Let me know if you have any questions. I'm an Eagle Scout and I have 4 sons who are Eagles so we have covered a lot of Scouting ground.