One of the keys to memory is conscious observation. As a writer, being able to remember things comes in handy -- as it does in many other professions. You can pass a place a hundred times and never take note of what color it is, because you never bothered to mark it: It isn't information you need. Even if you do, it might fade unless there is a reason to need it. Short-term memory and long-term needs aren't the same, else you could remember every phone number you ever looked up.
You can train yourself to do these things until it becomes a habit, if it is worth the time and energy.
I have a pretty good memory for faces, but not for names. If you meet a lot of people and you aren't apt to see most of them again, knowing the name attached to the face is less important and it burns up dendrites. I usually figure that if I keep bumping into somebody, I'll need to know their name, and eventually, I'll learn it.
There's no rule of thumb I apply, I just go with the flow.
Observation is also a good thing for cops, soldiers, bouncers, doctors, reporters, and even old martial artists trying to think tactically. I was in a fast food place recently and intent on my burrito, but as an exercise, I counted the number of employees working out front, the number of diners, where they were seated, and how many were men, women, or children. Took about two minutes as I chowed down. No reason I needed that information, but had a reason arisen, I'd have had it ...
I usually mark the exits of a building when I go into it. If there's an emergency or the Chinese army barges in and blocks the front door, I want to know how to get out. This comes from a time when I was in a department store that caught on fire and burned to the ground. One guy, trapped, ran into the bathroom and started running water. A fatal mistake.
In that case, I didn't worry about how to get out because there was a wall of glass and lots of things I could use to knock a hole in it. But that's not always the situation.
My second fire story was when my son was a baby and we were living in L.A., upstairs in a four-plex apartment. The next door neighbor, a ... lady of the evening, was entertaining a guest late one night and they set the place on fire. I awoke to the sounds of her screaming "Fuego!" and the smell of smoke.
We were on the second floor and there was only one exit. I went to the door, but it was stuck. I had a moment of panic. I pulled harder on the door -- and learned that hysterical strength is not a myth. The door frame kind of shattered and I ripped the door from it, hinges and all. After I got my wife and the baby down the stairs, I went back and started throwing our stuff out the window. By the time I had all our clothes out, the smoke in the stairwell was too thick to try it, so I went out onto the nice pile of padding I'd made.
In the end, we could have left the door closed and we'd have been fine -- the FD got it out pretty quick. As it was, we got a lot of smoke damage because some fool had ripped the door off its hinges ...
Odd what sticks with you once you learn it. When I was a private eye, I got pretty good at tailing and surveillance. One of the adjuncts to following somebody is that you begin to look into the rearview mirror more often. Not that anybody had any reason to be shadowing me, but if they were and winging it, no bugs on the car, and nobody to switch off with? After two turns behind me, I'll notice. No use for that in particular, but even thirty-five years later, I still have that habit.