For some players that have thick, short fingers this is often an issue. Even some players with longer and more supple fingers also too have this problem. It doesn't matter either instance...it is curable. I posted this exercise that I teach my students on another post for a different purpose, but it is also very useful for a 'redundant pinky' problem:
This is a simple ascending and descending scale in the key of A-major that uses the Ionian major mode. Play the notes with the fingers that I have indicated in red. Try to keep the movement of your hand position on the neck to a minimum:
1 4 1 2 4 1 3 4 3 1 4 2 1 4 1G -------------------------------------------------------------------
D ---------------------------4--6--7--6--4------------------------
A --------------4--5--7------------------------7--5--4------------
E -----5--7--------------------------------------------------7--5-
Now try playing the same scale and mode, but using this shape instead:
1 3 4 1 3 4 1 2 1 4 3 1 4 3 1G -------------------------------------------------------------------
D ----------------------------6--7--6--------------------------
A ----------------5--7--9---------------9--7--5------------
E -----5--7--9--------------------------------------9--7--5-
Notice how you have to stretch your pinky a lot more playing the second shape. You may notice that your thumb arc is a lot more extreme and your wrist is doing a lot more work. You may also find that your hand position is naturally starting to travel up the neck. Even though the second method is a bit more laboured it does give you better hand positioning if you want to explore more notes further up the scale and further up the neck. The first method is better if you want to travel down the scale to play lower notes.
This is another good exercise that I learnt when I first started to play that you may find helpful. It helps you to position all your fingers accurately and it helps to bring your pinky into the game and co-ordinate it with the rest of your fingers :
1 2 3 4 1 2 3 4 1 2 3 4 1 2 3 4 1 2 3 4 1 2 3 4 1 2 3 4 1 2 3 4G --------------------------------------------------4--5--6--7----------------------------------------------5--6--7--8--
D -----------------------------------3--4--5--6----------------------------------------------4--5--6--7-----------------
A --------------------2--3--4--5----------------------------------------------3--4--5--6--------------------------------
E -----1--2--3--4-----------------------------------------------2--3--4--5----------------------------------------------
You can repeat the same shape by going up half a step each time until you get up starting the shape on the 12th fret. Once you are comfortable playing this exercise without hitting any bum notes you can then play it backwards descending or ascending up and down the neck using the same fingering, random positions and random strings on the fingerboard...lots of ways...have fun with it! It doesn't make much musical sense and sounds a little silly when you are playing it, but this is just an exercise to help your finger and hand positioning as well as making use of your pinky. I still use this exercise as a part of my warm up before I perform. If you want to watch a good video of this in practice follow this link:
http://www.gospelchops.com/index-2.html then scroll down to VIDEO LESSON - "Bass Exercise" with "Booyah" Richard. He show's you another practical exercise you can do using the same method I have illustrated.
As you further your playing experience you will start to develop a playing technique that better suits both your physical abilities and your style. Your hand and finger positioning will alter depending on where you hand is on the neck, what you play and how you want to play it. As I have said, there is no right or wrong method. Just be sure you choose a method of playing your shapes and progressions in the way that makes you feel comfortable. Practice your scales and modes as much as possible and explore all the different shapes you are able to play, but keep your pinky available. When playing fast it is hard to keep your pinky on the fingerboard and you end up missing notes, which of course is not good. Practice these exercises slowly at first and gradually pick up the speed. It takes time and it's also a psychological as well as a physical thing...like using a 5th limb you never had before! Keep at it...you will introduce your pinky into a lot of your playing before you know it!
God Bless.