Easy Tips for Kids Brushing – Pediflor Kidz
Children above 2 years Brush teeth thoroughly, preferably after each meal or at least twice a day for two minutes or as directed by a dentist or physician.
  Use only a pea-sized amount of toothpaste; supervise child's brushing to minimize swallowing.
Children under 2 years Ask a dentist or physician.

Brushing Technique:

Fone's Technique For Children

Brush is firmly pressed against the teeth and gums with the bristles at right angles to the outer surface of teeth and the handle parallel to the chewing surface. The child occludes the teeth and the brush is moved in a circular motion with as large radius as possible. This technique is effective for young children.

Once children are older, the following method is recommended:

Outer surface
Inner surface
Chewing surface
Inner surface of front teeth
Outer and inner surface:

Place toothbrush at a 45-degree angle; start along gum line; use gentle, short, tooth-wide strokes against the gum line.

Chewing surface:

Hold the brush flat and brush back-and-forth.

Inner surface of front teeth:

Tilt brush vertically; use gentle up-and-down strokes with toe of the brush. Brush teeth long enough to thoroughly clean all tooth surfaces.

Don't forget to brush the tongue. Use back-to-front sweeping motion to remove food particles and freshen-up your child's mouth.