People might think that past life memories are something standard.  The truth is that everyone remembers differently, just like how it happens with current life memories. Even though past life memories share certain characteristics (read "Real Memory or Wishful Thinking" for more information) there are different types of ways we can remember.

 

I'll list the most common here:

Dreams: Many people remember their past lives through dreams, without them having any previous conditioning in regards to what they see or what they will remember. There are three types of past life dreams, and you may experience all or just one of thoese types of past life dreams depending on your personality.

Your dream could be a straight past life memory. You see yourself as something/someone else, your surroundings are different, you cannot control what happens in the dream and is like just watching a movie about your past life from the first person. In these dreams everything is pretty much accurate and no fantasy is involved. Things look like they looked back then.

Another type of past life dream is the informational type. In this kind you just "know" things.  You could just dream of the information as if somebody was telling it to you, or you can dream that you watch a movie about it or that you read the past life information in a book.  It wouldn't be strange either if you see the events in the third person.

A third type of past life dream is the hybrid type. This one is a mixture between both informational straight past life dreams...and a mixture between past life and fantasy. For example, you can switch between past and present, be in your room but your room is at the same time your past life office, things of the like. 

Needless to say, all types of dreams would have to be subject to validation afterwards to prove being past life memories and not just fantasy. A few people are experienced in lucid dreaming, that is, being able to control what happens in your dream and what you' re going to dream. For example, let's say you "program" yourself to visit Egypt when you fall asleep.  While dreaming, you realize you're in Egypt, so you consciously go visit the pyramids. It would be something like that.  However, this is just informative since I don't know how to do lucid dreaming, so I cannot give you any useful advice and it's not really the intention of this article, either. However, there are plenty of resources online on how to do it.

Flashes: You say you have "a flash" when, out of nowhere, you get a past life image in your head that lasts a few seconds but you can tell (by previous experience usually) that is past life-related. You can get flashes while being awake just doing your regular life things, or when you are really tired and you' re falling asleep.

Visions during meditation: Quite a few people get past life memories while meditating. They are pretty much like dreams except you are a bit more conscious while having them. 

You just know: Some people "just know" things. They are not too sure where the knowledge comes from, it's just information they've always had. Here are two examples: One are little kids that have obviously not been exposed before to certain knowledge, but they know about these distant towns and when they visit them with their parents, they can tell them information about the places. Another example is something that happened to me. I was watching a movie that took place in the 60's in Argentina, and in a scene somebody took a bus and the doors automatically opened. I said immediately, without thinking "That's not how the doors were!  You had to open them manually back then!"