This is how to prepare your hands to play the bass guitar. Before I even start playing I make sure I wash my hands, clip my fingernails, make sure everything is ready for me when I get started. I like to keep my hands warm all the time; in the winter I definitely wear gloves everywhere I go because these are really important tools. Once you're actually playing the instrument; once you're actually sitting down to play, I do stretches. I don't like to pull on my fingers or pull them back in any way. But just any stretch you can do where you don't have to actually pull back on a body part or a muscle group. You can just put your arms straight out, stretching your wrists with your hands up and down. And maybe even just shake your wrists out. Similarly, with the small muscle groups in your hands, you can just stretch your fingers apart. You can feel the stretch, especially between your thumb and index finger. And just pumping your fingers back and forth, open and closed, will get blood flowing into your hands. Once you've done all that, then you're ready to play. You can start by playing long tones, slow notes; just take it slow at first and don't jump into playing the fastest thing you know how to play. Often time when we're playing bass we're using small muscle groups that we don't normally use in other walks of life. You may have never used some of the muscles before that you're using to start playing the instrument. Take it slow, give your muscles a chance to get used to the new tasks they have to do. The small muscles have to learn to build. And you'll also need to develop callouses on your fingers. There's a simple exercise I use to build callouses just besides playing the bass, and it will happen naturally. But if you have blisters or callouses the easiest way to just build a defense so you can play for longer periods of time is to rub your fingers along the strings. I use these 2 fingers on my right hand to play mostly, so I just rub the tips of my fingers along the string. It actually just sends calcium to the ends of your fingers into your skin and will get your fingers a chance to prepare themselves to play the instrument. Similarly, with the left hand, you can press all your fingers along the string and run your fingers up and down along the string. Any string you choose, or all of them. And that motion itself, even though it doesn't feel like it's doing much at least prepares your fingers to let them know they're going to need to protect themselves against whatever you're going to put them through. Last I just want to mention pain. Sometimes when you're playing and you're learning new positions and you're teaching your fingers to do new things, you're going to experience pain somewhere in your arms, in your back, in your hands. If you ever feel pain you should stop playing. A lot of this stuff takes years to develop and pain is just your body telling you that whatever your doing is bad somehow or basically wrong. So stop what you're doing, rethink how you feel, stand up/walk around, and come back to the instrument, and just give yourself a lot of time and be patient; be patient with yourself and with the bass.