The Tree of Life is a map to the spirit world. Knowing your place and not being lost are just as important if not more so when traveling the spirit world as opposed to the physical world. Organization and awareness give you better control and better access to your inner power.
Feel free to explore the Tree of Life. Remember to ask your spirit guide to guide and protect you on your journey. Start drumming, relax, close your eyes, and envision a tree. The one I normally see is massive and towers far above me. I can feel that its roots stretch out far beneath me. Some believe that the trunk is square with one side pertaining to each direction. Exploring the trunk, the Middle World, will help you find answer to everyday problems that you may be facing. East tends to deal with beginnings, South with growth and productivity, West with completion and change, North with hidden things, thoughts and rebirth. If you have any questions or a specific problem ask your spirit guide to show you where to look for the answer.
After you explore the trunk and become familiar with it and how to find what you are looking for with it (which should take several journeys, learning takes time you know), you can move on to either the Upper World or the Lower World. I would suggest you make yourself comfortable with the Upper World before you move on to the Lower World. The Upper World, in the branches, is the area of creativity and the future. If you wish to divine the future this is the place to learn. It is also the realm of flight.
The Lower World, the Underworld, the roots of the Tree of Life is a very powerful place and there are some dangerous things there. Remember to always bring a guide with you to the Underworld, just to be safe. This is where you can commune with those who have passed on or find information that you have lost. It is also the place of the physical body and survival. This is where you can learn healing and the secrets of the body.
It is best if you are comfortable in all three worlds. That way you will know where to go when you need specific information. Always return the way you came and always thank your guide for their help and protection.