Jack Canfield, author of "The Success Principles" and co-author of the "Chicken Soup for the Soul" series says mastermind groups are “one of the most powerful tools ever used by successful people.”

Mastermind groups are used by Anthony Robbins, Mark Victor Hansen, John Assaraf and many others.

Napoleon Hill, author of the famous book Think And Grow Rich, is credited with first describing the "mastermind principle." (see video below)

DEFINITION: 

Mastermind -- Two or more minds working actively together in perfect harmony toward a common definite object.

Mastermind groups are simple and yet profound.  Simple in that the uninitiated might see them as "support groups".  Profound learning and growth is what comes out of them.

If you want to be a strong leader then you need to experience the power of a mastermind group.

I've been a member of several mastermind groups and I facilitate others.  Christine Kane offers these 7 tips for creating a successful mastermind group.