Punching bag routines are a great way to train your body to perform boxing combinations. Hitting a bag teaches good form. Punching in combination increases muscle memory. Your body will instinctively repeat the punching motions without hesitation even when you are not hitting a bag.
Start with a jab punching bag routine. Move in a circle around the punching bag while shooting out jabs as fast as you can. Do not punch with power. Focus on speed and movement. Arc around one direction and then repeat in the other.
Do a "left-right" punching bag routine. This can be "right-lefts" if you are left handed. Start by throwing a fast jab at the punching bag then immediately follow with a hard straight punch with the other hand. The straight punch should be generated from the feet and hips for power. Do a series of these to get a feel for the timing. The punches should be quick then hard.
Perform a body shot punching bag routine. These punches are aimed at your opponent's ribs. To sneak them under the guard, bend your knees slightly and circle your punch from waist level. Straighten your knees and swing your hips as you strike the punching bag. The routine consists of a series of lefts and rights to the center of the punching bag. Focus on bending your knees and raising up with every punch.
Do a 1-2-3 punching bag routine. This consists of a quick jab followed by a hard straight punch with the other hand followed by a body shot with the jabbing hand. All the punches should be performed in quick succession without sacrificing form. A 1-2-3 punching bag routine should be done after warming up with a left-right routine and body shot routine.
Do a 1-2-3-4 punching bag routine. This is just like the 1-2-3 punching bag routine but has an uppercut added at the end. An uppercut involves a punch coming straight up toward an opponent's chin. This requires a deep knee bend and hip turn so the fist can rise at a low angle. A 1-2-3-4 punching routine requires a lot of coordination since you are performing four distinctly different motions right after each other. Start slowly then speed up as you become more comfortable.