Shadow boxing isn't just throwing punches; a lot of the old-time trainers and fighters thought that it was the most important part of training. The idea is to educate your mind by fighting a real (if visualized) opponent. So you want to move around the ring- trying to cut him off or to avoid being cut-off- and slip punches, duck, bob-n-weave, and so on. Do everything as if it were a real fight; at speed, punching and moving sharply. To my way of thinking it is a better way to begin a workout than jumping rope because it exercises your mind...if you let it.
That said, everything works around the jab-straight right-left hook combination. Move the hookto the head or body, double up on it, follow with a right uppercut, whatever. The important thing is to finish your combinations with a left-handed punch because that gets you back on balance. AND...set up your punches. Imagine an opponent that doesn't want to get hit and that is trying to hit you: slip inside, throw a couple punches and get out.