Three exercises/skills to help improve your skills

Bounce Pass - A good weighlifting exercise for this   movement would be Tricep Pushdowns with a cable and a rope attached to it.  This should help develop the tricep muscle as it pronates the weight and will help exert more force and velocity behind each bounce pass you do.

Chest Pass - Close Grip Bench Press is an excellent way to help you with better, more faster chest passes.  By using close grip when benching it helps target your chest along with a lot of tricep motion due to the closer than normal grip.  This helps gain explosiveness in both muscle groups while also helping you develop muscle memory in other areas.  This should 100% improve your chest passes and explosion.

Overhead Pass - Dumbbell Rotator Cuff Exercise - This exercise is a very good way to help prevent injury more than anything.  It helps stretch out and keep your shoulder muscles loose.  By keeping your elbows locked in a pronated position it helps focus more on the shoulder muscles working together.  This should help lossen your shoulders up before attempting any overhead passes and help prevent any shoulder injury.  However, injuries do occur, this exercise should help speedup recovery and can also aid as a rehab recovery exercise for people who may have shoulder problems or injuries.

Skills

Skill #1 - Stand a few feet from a wall and focus on an aiming point at the ground.  Once you have located that spot, bounce pass the ball at that spot so the ball hits the aimed target then bounces off the wall and back into your hands.  Repeat this until you get comfortable with your aiming points for bounce passing.

Skill #2 - For chest passing,  you can also stand close to a wall or a partner, a medicine ball is optional.  Once you are near a wall or close to a partner,  hold the ball in tight close to your chest and explode exerting energy from your triceps and pushing the ball away from your body.  the faster you push the ball away from you the faster the ball will come back to you and will increase your number of reptitions.

Skill #3 - For an overhand passing skill you can practice inbounding the ball from the sideline, however, if you do not have a partner with you you can stand at the near foul line or half court and overhand throw the ball so it bounces off of the backboard and comes back to you to avoid chasing after it and decreasing your number of reptitions.  For advanced players you can quickly catch the passes off of the backboards and turn 180 degrees to the opposite backboard and repeat the same skill to add in some quick movements to your skills.

Steps to the Overhead Throw

Step 1:

Keep ball located right behind your head so its difficult for your defender to get a hold of it.  Locate your target and get ready to throw

Shoulder Girdle - Your left and right shoulders are both in abduction supernating with internal rotation about 100-115 degrees vertically.  Your pectoralis Major is also contracting concentrically.

Elbow - Your left and right elbow joints are both in abduction in flexion 95 degrees over your head.  Your biceps Brachii is contracting eccentrically while your triceps are contracting concentrically.

Wrist - Both wrists, hands, fingers and thumbs are in flexion with the Flexor Digitorum superficialis with the flexor pollicis longus contracting concentrically.  Both wrists are eccentrically contracting their flexor carpi radialis 

Step 2:

Begin to launch ball over your head towards your intended target

Shoulder Girdle - Both shoulders are abducting in upward rotation while contracting eccentrically.

Elbow - Both Elbows are flexion while the Biceps Brachii is contracting eccentrically and the Triceps Brachii are contracting concentrically but are slowly starting to begin eccentrically contracting.  The Anceous is contracting eccentrically.

Wrist - Both wrists, hands, fingers and thumbs are in flexion with the Flexor Digitorum superficialis with the flexor pollicis longus contracting concentrically as they are getting ready to release the ball away from their body.  Both wrists are eccentrically contracting their flexor carpi radialis 

Step 3:

Keep arms extended with a little lean at the waist to give extra momentum and force behind the throw

Shoulder Girdle - Both Shoulders are in forward rotation and are both in abduction 90 degrees from bodys Torso and parallel to the ground horizontally.  Your pectoralis Major is contracting eccentrically after release of the ball.

Elbow - Both Elbows are in extension the Triceps Brachii is contracting eccentrically and the Biceps Brachii are contracting concentrically.

Wrist - Both wrists, hands, fingers and thumbs are in flexion with the Flexor Digitorum superficialis with the flexor pollicis longus contracting concentrically.  Both wrists are in extension eccentrically contracting their flexor carpi radialis, and Palmaris Longus and Flexor Carpi Ulnaris

Overhead Throw Video

Overhead Throw Video

Steps to the Chest Pass

Step 1:

Keep ball clenched close to the body and away from any defender

Shoulder Girdle - Both in abduction pronating with upward rotation holding the ball close to the body parallel to the ground.  Your Pectoralis Major is also contracting eccentrically as the Pectoralis Minor is concentrically contracting.

Elbow - Elbows are in flexion as the Biceps Brachii are contracting eccentrically and the Triceps Brachii concentrically contracting.

Wrist - Both wrists, hands, fingers and thumbs are in flexion holding the ball tight and close to the Pectoralis Major and Pectoralis Mnior with the Flexor Digitorum superficialis with the flexor pollicis longus contracting concentrically.  Both wrists are in flexion eccentrically contracting their flexor carpi radialis

Step 2:

Push the ball away from your body in a linear motion parallel to the ground

Shoulder Girdle - Your left and right shoulders are both in abduction supernating with forward rotation about 90-100 degrees horizontally from the ground.  Your pectoralis Major is also contracting concentrically.

Elbow - Elbows are in flexion as the Biceps Brachii are contracting eccentrically and the Triceps Brachii concentrically contracting but slowly going to begin contracting eccentrically..

Wrist - Both wrists, hands, fingers and thumbs are in flexion with the Flexor Digitorum superficialis with the flexor pollicis longus contracting concentrically.  Both wrists are in flexion eccentrically contracting their flexor carpi radialis