Some religions make the idea of reincarnation central to their belief system. Whether or not that applies to you, being open to the possibility that you have been on this earth more than once will increase the chance of a successful session.
2. Get a good helper
Often our past lives bring up emotional responses. You need to make sure that the person you are performing the journey with - the person guiding you through your past - is capable of helping you if emotions come to the surface. If you are using a guided MP3 then make sure that you are near someone who can help if need be.
3. Realize that your memory is fallible
If you're like most people, you probably don't remember what you were doing this time last month or last year. Consider that if a memory as recent as a few months can be hazy - and that memory is from this life - then one from a previous life can be even hazier. This means that you may need several practice sessions before you start to get results.
4. It's not television!
Don't expect crystal clear pictures of your past life. Apart from anything else, you'd probably be locked up if this was the case. Take the time to get a sense of what is happening. Chances are that your past life session will guide you through this. You'll likely be asked what (if anything) you're wearing on your feet, what smells you are experiencing, that kind of thing. It's a good session if you can get the essence of these feelings. It's very unlikely that you'll see yourself in full glowing Technicolor with Dolby sound!
5. Spirit guides can help
Depending on the method you're using, there's a likelihood that you will have a spirit guide to help you through the experience. They can offer helpful insights and literally guide you through the experience. A good regression will help to bring out your spirit guide. If you've already met your guide in another experience then this part will come fairly easily. If you haven't, take the time to get to know your guide. They're often called "angels" and many people believe they help us in all aspects of our day to day lives.
6. Apply the experience
Quite often a past life regression will be related to a current problem you are experiencing. This is more likely than you may think. After all, we're talking about one or more likely many past lives. You'd have to have lived like a hermit in every single one of these for there to be nothing that was relevant to whatever it is you are currently experiencing. Apply what you learn in your past life journey to whatever is currently happening in your current life.