I keep an Excel document with the following worksheets in it:

-Ship registry
-Ship classes
-Fleet OOB
-GU OOB
-Beams
-Missiles
-Electronics
-Engines
-Terraforming
-Leaders
-Class names
-Requirements (Tech components for specific Fleet needs/vessels)
-Manufacturers
-Maintenance (this is per individual unit of each class)
-Fighter Squadrons

This enables me to get straight back into a game even after a long break plus makes things easy if I write a little RP/story around something.

Naval OOB:

Christ almighty this is some weapon grade autism right here ..... i love it <3

I keep a log when I'm doing a fiction writeup, and another file with research, things I might add, etc.
I should point out that the ingame event log is dumped periodically onto your hard drive, I have trouble finding it sometimes, but the log for my current game appears to be shoved into C:logs. There's a file in C:\logs named after the game, but the logs are just dumped in C:\logs not in the game's proper folder.
That log does contain NPR and spoiler information though so you shouldn't really use it, what I generally do is sent the event log to thousands of displayed lines so that generally it scrolls back a few years for reference anyway, then as I run increments I add basic info to my notepad, and do the writeup at the end of the year.

Not a log, but I do keep a text file with notes on things to do and things I need to remember when loading the game next time after a week of filling my head with work. I consider it a good sign when I need to do that. The last game that comes to mind where I did this is Nethack.

Most of the games that I have started so far, have either been pure attempts at learning how to play Aurora, or enjoying the game as a game. In my current and last game, however, I have been able to keep my empire alive and well for a longer period of time than before, more than 40 years. In my current game I'm a few years away from 50, which is a record for me, even if it might not be all that much for some of you veterans.

I have also started to enjoy the story of my empire throughout those years, rather than simply as a game. I have at the same time realized that I really wished I had kept a log throughout those years. Being able to look back at and knowing how old a colony is, when the first military fleet was finished, when research and development started on the new generation of military ships, when a star scientist died, when you were at war, etc. really does seem to add a lot to the experience. I am certainly missing the ability to do that right now, and expect to start such a log with my next game.

But this consideration made me really curious as to whether this is standard practice as part of the Aurora experience. Judging from the many after action reports and works of fiction it seems that at least some people do it. But I am curious to see how many actually do it, and if you do it differently depending on what kind of game you expect to have.

And thus follows a poll