Astro- travel can be done in several ways and not always with a guide. Depending on who you study it from sometimes guided meditation is considered astral travel. However the way I was taught was that there are several kinds: ( I am not going to list all of them because I really dont want to write a novel)
1. Guided Meditation - a form of astral travel done with a speaker or music giving direction to a person or group of people who mentally walk the instructions given. These are often done as a training technique for other types of astral travel as well as a way to help focus the mind.
2. Shamanic Walking - (there is a better name for this but I cant remember it off the top of my head.) Where one after meeting an animal spirit guide is then shown or taken to places and things in order to teach a lesson.
3. Astral-planeing - The act of one falling asleep and then in dream mode (this requires lucid dreaming btw) falls asleep and then wakes themselves on a astral plane and and explores to learn things and to meet others.
4. Astraling - The act of mentally walking around ones plane of exstistance out of body.
I have done all of thee above and all the rest (with the exception of the "little death" style which is unsafe and unhealthy since it requires the person to put their body in a coma). Guided meditation is by far the easist and safest. I was taught that when astral traveling to always leave a thread of myself attached to my body so that I could find my way back. While it is hard to prove the reality of it I have known people who have gotten lost while trying it, lucky for them they found their way back.
LH