My memory is generally crap and hasn't gotten better with age. Though I've recently noticed I have acquired quite a skill for memorising longish random passwords and number sequences quite well, getting better at it over the years. No deliberate technique to it, just consistent practice forced by paranoid security and compartmentalisation.
A friend passed on to me the knowledge that the skill of "what were we just talking about" can be improved dramatically with effort. (Indeed even under the influence of certain substances which significantly impair short term memory!)
The secret? "Just try remembering a little harder."
I went from being totally crap at keeping track of conversations, to significantly above average, by just forcing myself to try and remember a little harder, every time I forgot what we were talking about.
(I don't know about other types of memory, but one proved Surprisingly Trainable.)
Yeah it happens naturally with anything you use a lot.
When I was in high school I knew dozens of phone numbers. Today not so much (though I still remember the number we had at the house where I grew up, and a few others that were for my good friends).
> I still remember the number we had at the house where I grew up
One of my earliest memories is of my mother drilling my brother and I on our telephone number. She did a good job. I'll never forget it: AMherst 3-7004.