There are several methodics of regression. But you can't do this without help of a person who can do it - your Guru. I've passed through a good course of esoterics in previous decade.
But I can say also that not so many people have the ability of regression memory. For eg. out of 200 people it may be only 3-5 who will have the real reminiscences of past life. The other may be only some kind of illusions. It is hard to define them out of simple dreams.
Regression technique is use in psychoanalysis for remembering childhood events that have great impact on your neurological behaviour.
Many times it is seen that what comes out is not relevant and useful, but only trash.
For previous births can we be sure that what comes out by regression is correct?
How the authenticity of information is established?
The ability to remember the episodes and events of past is one of interesting processes - memory is somewhat mystical. As well as the gift of foreseeing.
For eg if you try to remember the previous day - you'll find out that this process is somewhat hard and demands some kind of work of your mental activity and mind. When you try to remember the events for eg. in the previous year on the same date, you'll find that sometimes that is impossible. And the farer in the past - the lesser are the reminiscences. And the earlier years, when you were a child - is out of memory at all. The more harder is to join the events of present and previous lives.
This work is the work of energetical centers - ajna - sahasrara. When the lower centers are in bad condition - the memory is also bad. So you can't remember the previous life without the help of the person who has great energy and developed Hara center. The ordinary people have not so much energy (especially in lower centers which are responsible for daylight activity) and dim aura. I've seen not so many people with good aura. They are so rare in life. But of course many of them are the outstanding persons in life - academicians, directors, artists, presidents, saints.
The regression is not only the remembering of events of the past, but also the ability to use the knowledge in your life - the lesson of GOD, who tries to show you the roots of your mistakes and successes in the life.
From my experience the regression is similar to the process of remembering (may be with open or closed eyes), just the same. But there is the other life, other conditions, other nation. And this reminiscences may be not only one day but for months. You see the repeated dreams with continuation. Sometimes it is hard to stop this process. "To keep the roof clear". The orientation into the past may become an obstacle to your present life. That was with me some years ago. Today is better. To forget is one of the favour of God. But how you can estimate this, if you haven't passed through such experience.
To control this process - is to control your mind, behaviour, activity. Your abilities become the ruler of your life - you can't be the same as the others. You can't think as the others - you've seen the river of time - the flow of your life.
We have been every type of person imaginable in our previous lives:
from lepers to powerful kings & queens -
from mllechas to brahmins -
from yogis to politicians -
.................
Rebirth can be a very painful experience,
especially since most of us have no control
on where-when we take our next body.