It depends on what you believe about past lives and past selves. For some, it is entirely possible to remove oneself enough from this life or to delve into their soul to the point that they view their other lives in sequence. (It sounds a bit fluffy, but if you've ever seen the Avatar series on Nick, when Korra or Ang speak to the previous avatars, it's similar to this.) For others, such as myself, an experience of a past life is easier to work with when viewing it as that person and experiencing as they did rather than speaking to them.
You would have to go into a lot of trance work and projection work, and probably have to make up a few creative ways to explore the different lives that are within your soul (or a part of it depending on belief). But these two things would be helpful in my opinion. :)