I often forget certain things from the past that others remember, i find pictures i good way of unlocking memories.

The last time i met up with an old school friend she started talking about a couple of kids that were in our year and a particular event that had happened at school, i didn't have a clue who she was talking about, so we dug out some pictures and it all came flooding back.

I've heard of various methods of improving your memory, but I think that would only apply to better remembering things in the future.

As for the past, try the poor man's psychoanalysis, long talks about the past with family and friends.

I'm not sure what one can do to improve the recollection of past events. Maybe some form of association may work if you have an idea what it is you need to recall the detail of. For example, my recall of names is quite bad; I find just saying the letters of the alphabet in my mind often enables me to recall the name I need to know. This is a fairly trivial example of association but you may be able to build on it.