Meditation is usually the method most people use to get past life memories. There are numerous ways you can meditate.  Here we´ll just mention the most common one.

It's recommended to eat light before doing this and not be too tired. During the day you'll have to think that you will succeed and remember your past life.

To start, you have to lie somewhere comfortable, and concentrate on relaxing your body. Mentally review all of your body parts and check that they´re relaxed. Start with the feet and move up, finishing with the head. You will start feeling ticklish, that's good, it means you´re doing it right. Once your body is completely relaxed, you will concentrate on your breathing,. You have to feel the breath and pay attention to it. At first take a deep breath and exhale, this is to  get more relaxed, then start breathing normally. Later take a breath, keep the air within a few seconds, and exhale (this is called "breathing in three times"). What do you do with the mind in the meanwhile? People say, "Don´t think about anything--keep your mind blank." However, we know that's impossible and the mind is always working. What you need is to give it a chew toy, a mantra, for example.  Repeat the same word over and over again---it can be your name, or any phrase that means something to you.
If you do all this correctly, memories or images will start coming to your mind.  You will realize it's not just your imagination because you're not making any effort, they just come like  lightning and you can`t stop them. Don't analyze them immediatly or you'll lose concentration. Once you finish, write them down. It´s also recommended to not have expectations about what you will find during your meditation.
If it helps you relax and you are good with images, you could try some visualization techniques at the beginning or your meditation. A visualization technique is something symbolic that could help you lift mental blocks. For example, imagine that you are breaking a wall, or that you go down the stairs: Every step you go down, you get more and more relaxed.

Possibilities are endless. To list a few, you can imagine:

You are in a library with many books and many rooms. Some rooms are dark with books that are old and dusty.  Other rooms have light and the books are clean.  The books are your memories and the rooms are your lives.

You go through a dark tunnel with a light at the end. When you pass the light, you´re in a room with many doors, each door taking you to a different life.

You can also try these visualization techniques before going to sleep to see if you can get past life memories in your dreams.

If you think you need guidance, an extra boost, there are always guided regressions online that you just have to listen to and do as they say. Here is one we recommend: