An often overlooked aspect of hand and grip strength building, is hand dexterity exercises. It is important to exercise the hands in order to stretch and strengthen its joints and muscles, and also work on flexibility, coordination and range of motion.
One of the simplest hand dexterity exercises that you can do on a regular basis no matter where you are is the finger flex. Hold your hand in front of you and make a fist, then slowly open your hand while stretching your fingers out at the same time. This will work on your finger joints, and can be repeated several times with each hand.
Another exercise that is useful also helps to improve hand and eye coordination. Start by holding your hand out in front of your chest with your fingers extended fully and slowly move your index finger to your thumb so that your fingers form the letter o, or the informal sign for a-okay! Hold for a few second, then flex the index finger back to its extended position and move the next finger to the thumb, repeating the process with each finger.
Continue with each finger, increasing your speed so that you are moving through your fingers fairly quickly as a way to help improve coordination.
Another exercise that will primarily benefit your thumb begins with holding your hand in front of you with your fingers grouped together and your thumb extended to the side of your hand. Slowly extend your thumb out so that it crosses your palm to reach the base of your pinkie, and hold for about 5 seconds. Slowly return your thumb to its original position and repeat the stretch 10 times or more. A basic hand dexterity exercise for the thumb can be performed at will no matter where you are several times throughout the day.
You will want to flex and stretch each finger as well in order to improve hand dexterity. One way to do this is by holding out your hand with your palm facing you, your fingers upright and together. Stretch all the fingers at once in a single, slow downward motion until they are pointing toward the floor. Then, slowly reverse the movement as if in slow-motion, so that you fully extend your fingers back to their original position.
Other simple ways you might try to improve dexterity is to write with your left hand if you are right handed, or vice versa. Or, pick up a pen or pencil without using your thumbs and try writing with it using only your fingers. Musicians must have extreme dexterity, and some of the exercising involved in learning to play the piano, for instance, can be useful exercises in improving coordination.