Ruby Slippers

At the end of the Wizard of Oz, after many trials and tribulations involving talking scarecrows, flying monkeys and a few song & dance numbers, Dorothy learns that all she needs to do to get home is to click the heels of her ruby slippers together and say, "There's no place like home" three times. All the while Glinda, the Good Witch of the North watches over Dorothy and guides her on her journey back to Kansas.

When the scarecrow asks Glinda why she didn't tell Dorothy earlier what she needed to do, the witch answers "Because she wouldn't have believed me. She had to learn it for herself".

Basically, the Good Witch of the North was the ultimate mentor - allowing Dorothy to make her own mistakes but ensuring that she was heading in the right direction to achieve her goal.