Start with one ball
in each hand and practice the 2 step throw and catch with each hand. It
is important that you learn to throw an nice even arc with each hand,
paying particular attention to making the ball land straight into your
other hand. Notice on the animation how you should throw under arm through
the centre. This is the easiest method to learn with.
Once your throwing is up to scratch move on to 3 balls. Start with 2 balls
in your right hand and one ball in your left. Throw your first ball and
just before it reaches its peak throw the other ball. Immediately return
your hand to the outer position to catch the falling ball. Repeat on the
other side and you're off.