Shamans live with a foot in two worlds, the physical one that we all know and the visionary or "spirit" world, the world of the imagination. Shamanism teaches how to bridge the gap between the real and the imaginary. The main tool of the shaman to this end is visualization, or simply put, their imagination.
Put the idea that imagination is useless make-believe play out of your head right now if you want to learn anymore about shamanism. It is not pointless mental activity and it is most definitely not just for children. It is the link to the spirit world. If you want to use Shamanic techniques in your life, get used to the idea of using your imagination.
Children can access the spirit world easily, but learn to block this ability as they get older. This is not a bad thing. Children need to learn the difference between the real world and the imaginary, but some people learn to shut it off too well and will need to relearn what they automatically knew how to use when they were a child. But don't worry, it's just like riding a bike, you'll remember very quickly.
Shamanic visualization uses all of your senses, sight, touch, hearing, smell, taste, and even the 'sixth' sense if you wish to use it. The more senses you bring into your visualizations the more powerful they will become and the easier your travels will be.
Here are some visualization exercises to try. They are in order from simple to more difficult. It will probably be most helpful if you work them in the order given. Remember after you complete an exercise feel your body and your heart beat and where you are sitting before opening your eyes. It can be jarring to be relaxed from practicing an exercise and then suddenly being back in the physical world without a moment to adjust.