As a referee, it's important to recognize that coaching, especially at the younger levels, can be particularly challenging. Many coaches have limited knowledge of the game and they are relying on referees to help them as guides through the game process. The important thing for coaches and referees to remember is that we are all volunteers and sometimes a friendly reminder of that can go a long way. 

When introducing yourself to a coach at the beginning of a game, throw in a "good to volunteer with you". That can help set the stage that you are both working together. There may be an occasion where you need to speak to a coach about a particular topic, and saying something like, "Hey, Coach, can I talk with you away from the kids for a second" can be helpful with many coaches.

We are all volunteers and we all need to be respectful of each other.