I put a question mark on the title because I cannot really prove the visions are related to past lives, but this is a fun way to guide people through a process to see what could be their past lives.
Each participant gets into a relaxed position, usually either sitting in a chair, or laying down, or otherwise sitting against something comfortable. Spend a few minutes leading the participants through a relaxation process, whereby they let their bodies relax and keep their minds awake. Once they are in this mind awake / body asleep mode, invite them to imagine getting up and leaving the room. Guide them to imagine traveling far away, whether by vehicle, or through a cave, or through a forest, or by any other means which takes them from the familiar, to the unfamiliar, and guide them to arrive somewhere new, yet familiar. Give the participants a chance to explore the familiar area, including seeing other inhabitants of the area and moving around and communicating with them. Once they have explored the area, lead the participants gently back the way they came, allowing them to have a clear memory of what happened and what they heard and saw. (say things like "coming back slowly, you clearly remember what you experienced," etc) Once their awareness focuses back on their physical bodies, give them a chance to write down what they experienced. Do not speak until everyone is pretty much done writing. The whole process is a state of light hypnosis, and everyone will still have full control and awareness of where their physical body is. They will be able to come back in a moment's notice if they choose. Each process will take about 20 or 30 minutes.