The committee chair is a position of varying importance in different units. In some units the SM is completely dominate. In most units the committee chairman takes care of the organizational parts of the troop and the SM and ASM's take care of the operational side.
If it is a new troop, you and the committee are responsible for finding the SM. In ongoing troops, you set the guidelines and make sure everyone adheres to those guidelines. With the committee, you might develop a code of conduct manual that covers acceptable behavior, uniform attire for meetings and travel (Exceptions for Scouts coming from soccer practice, etc.), camping guidelines, etc.
You chair the meeting (usually monthly) of the committee. You need to have a secretary, treasurer, advancement chm, and planning chm. You might want someone for camping, fund raising, etc. The more you can delegate these responsibilities the more you can manage rather than do.
If you go to the Scout store near you (or on-line) you can get some printed material to help you out. I would also get the Guide to Advancement- it will answer a lot of general questions for you.
Hope that helps. If you have some specific questions, I'll be glad to help.
