Your grip demonstrates your strength and power. Besides having a bone-crunching handshake, a vise-like grip will be helpful in doing bench presses, pull-ups, push-ups, deadlift and a variety of other exercises. You want to have a powerful grip to have along with a low body fat, ideal weight, lean muscle mass, and other attributes of physical fitness and physical prowess.
I remember the late Bruce Lee having tremendous and powerful forearms that came with a strong grip. For his size, Bruce Lee has to have one of the largest forearms in the world. According to his writings, he was focused on developing strong grips and power forearms. Here is a way to develop a powerful grip. This is a modified pull-up using towels. Before engaging on this very difficult exercise, you want to be able to do about 8-10 regular version of this upper body exercise. You will need to built your physical fitness level to get to that elite level. Get one of those portable pull-up bars so that you can gradually (I emphasis on gradually, or you can hurt your shoulders or elbows) get stronger on your pull-ups.
Once you are strong enough to do 8-10 regular version of pull ups; then, you may be ready to do these special version pull ups using 2 towels. So get 2 towels and place them over the pull-up bar at shoulder width apart. Then, you can do pull-ups by gripping on those towels. These will be very difficult. You can try to lightly wet the towels to get a better grip. Also, if this is too difficult still, then you can try one side at a time. Instead of two towels, use one towel. Your other hand is gripping the pull-up bar. Then, pull yourself up with one hand gripping the towel. When you are strong enough, you can use two towels. This will put an enormous strain and stress on your forearms because you are working on your grip- with your body weight pulling you down. These version of this classic exercise with towels will add variety to your upper body routines. You will also have an effective way to build the grip in your forearm. If you excel quickly where you start becoming stronger fast, you can then add a weighted belt and add maybe around 15 pounds on the belt for extra resistance. You can even cross your legs at the ankle and add a light dumbbell between your ankle for extra resistance and you do your pull ups.
As I mentioned earlier, these are challenging and you must get strong enough to do just a few of these exercises using just towels. Your grip epitomizes strength and power. Many times, you will be wishing that you had powerful forearms and a vise-like grip to win any firm hand contest, or any wrist wrestling matches. Pull-ups using towels can put a real grip in your physical fitness life.
Also consider using forearm grips sold mostly at sporting goods stores, perform standing behind the back wrist curls with a straight barbell, seated forearm curls on a weight bench with both forearms flat on the bench a few inches apart with your palm facing the ceiling with a barbell or a dumbbells and curling the weight with just your forearm muscles repeatedly, do weighted rope curls which basically has a straight bar handle which is about a foot long with a piece of rope attached in the center of the straight bar and it has plated weights that can be added at the bottom of the rope to use to curl the weights up and down to strengthen your forearms. There are several other machines at the gym specifically designed to give anyone a vise like powerful grip if they so desire it.