In short, you will need to balance each axis of your gimbal so that the centre of gravity of the camera falls through the axis of rotation of the gimbal (see the pictures below). This means that when the gimbal is turned off, the camera will will keeps its position if its correctly balanced.
Its important to balance your gimbal properly to get the best stabilisation out of the gimbal. If you are using powerful motors and a light camera balancing becomes less important, but its still usefull to balance everything properly.
This guide has been moved, please visit the Balancing your brushless gimbal post in the link below.