Meditation and scrying, as already mentioned, are the more effective and immediate ways to see into your past life, but it can take an abnormally large amount of time for your meditation pending your skill and recall, because sometimes our souls don't have a body for long periods of time after a life. Example, Emily was a priest in the BC times. She dies. She doesn't instantly reincarnate, her soul simply wanders, and after 200 years, she is incarnated. It can be hard to recall an event or series of events that could've happened 200 years ago.
Scrying would be effective I suppose, but you should have some adept knowledge in meditation.
I may suggest asking a deity that you may worship and maybe it will tell you. Another thing, maybe compile your own spell to seek your past life, as your own spells are more and just effective (usually) than those made by others.
One of the most common way of past-life identification is D?j?-vu when one encounters something similar to a past life in their current life, and a vision or a recollection of events hit you, and suddenly you remember the scent of the air, the way the rain felt as it dripped into that cut you got when working a sword with the blacksmith etc., but this isn't always available, and some recollect events of their current life that they've forgotten.