Hi Themword,
Everybody accesses past life memories in different ways, but here are the types of hints I pick up on...
words/names that come to me in my dreams, or in daydreams that don't seem to have relevancy to the present-day, or to my otherwise conscious thoughts.(I have learned to pay attention to this, because they can be subtle, and easily forgotten as nonsense, but can be very important in validation. For example, I was waking up one morning, and 'saw' the word GIEVE in my mind's eye...I was about to dismiss it, but decided not to. Letting myself think about it, I also realized the word appeared to be above a storefront, and about the same time I realized that, I could hear the echo of hoofsteps on cobblestones and 'knew' a horse-drawn carriage was going by...now after researching, this turned out to be a very strong validation/connection to a past life...I won't go into further detail, as it isn't relevant to your question...but yeah...pay attention...if you get strange words/phrases, either written or voiced.
I am more auditory, but along the same lines, if I see things in my mind's eye that are anachronistic, without any connections, that's a clue.
Strong attraction/aversion to other cultures/historical periods than my own present one.
Synchronicities/repeated themes/encounters with people/music/ideas that could convey some kind of past-life message
Then, obviously if you dream about events that are clearly anachronistic, but you feel that you are there or you feel very emotionally involved in the dream that would strongly indicate a past life memory
Hope this helps