To raise your Super Saiyan Bar to where you can transform quickly or
keep your bar from going down, you need to attack continuously so that
you don't give your opponent a chance to attack back. If they use the
Combo Breaker move, start attacking again and don't give up. The best
way that I have found to do this is to do rotations of 3 kicks and 3
punches. That way, you don't do a combo move and leave yourself open for
an attack. Keep it up and you will be a Super Saiyan in no time. When
your bar is full, power-up and you will change. If you are low on
energy, you have to power-up completely before you can change.

Note:When you change, if you don't keep attacking your SS bar will drop
and you wil turn back to normal.