Finger Exercises
Finger exercises for strength and dexterity on your fretting hand
I found doing specific exercises helps to strengthen all the fingers, including the pinky, on my fretting hand. When you begin these it's important to go very slowly at first. You should aim for accuracy of fingering and tone before you ever try to speed up. It really doesn't matter how fast you do these exercises, what matters is that you use the correct fingers and get a clean tone. So go very, very slowly.
Also, I don't recommend doing these for more than a few times at a time. Maybe 3 times through before you begin to practice other music and then 3 times through when you are done practicing other music. The goal is to slowly build up strength in the fingers on your fretting hand. This takes repetition and then rest. Just like any other strengthening exercise, you can't get to the strength if you strain the muscles by trying to do this too much or too fast.