Thumb Touch This exercise helps increase the range of motion in your thumbs, which helps with activities like picking up your toothbrush, fork and spoon, and pens when you write. Hold your hand out in front of you, with your wrist straight. Gently touch your thumb to each of your four fingertips, one at a time, making the shape of an "O." Hold each stretch for 30 to 60 seconds. Repeat at least four times on each hand.
Get a grip. No, really. Research shows a relationship between weak midlife grip strength and a decline in function later in life. (from @Patti Stamp) if you aren't into weightlifting, here are some other ways yo improve your grip.