I record as many specifics as I can.
That includes a separate bound book on the shooting bench as I fire those handloads, with range data regarding chronographed velocity, temp, winds, altitude, humidity, lighting conditions, etc. Bullet impacts do change with the environmental variables.
I'm looking for the best performance out of a given gun/ammo combination, with respect to accuracy, velocity, cleanliness, cycling, ease of chambering/extraction, and even thumping qualities come Bambi time.
I also have several obsolete and wildcat chamberings in my collection. I have to work up those handloads basically from scratch, because published data just isn't there. 29.0gr of AA1680 will give good accuracy out of a 7.62x45 Czech VZ-52 rifle. 27.0gr will produce keyholing from the same gun.
I run some serious loads out of my Desert Eagle. Accurate Arms was kind enough to list a separate load section for the gun in one of their volumes, otherwise I had to work them up myself when using WW296 or Alliant 2400.
Good documentation on my part lets me know when I'm on the right track for a wonderful load, and allows me to repeat that load, or not repeat loads that didn't work so great for whatever reasons.
So, yeah, I document my handloads, be it in a bound book, ammo box label, a computer database, or a combination of all three. I also document my available ammo inventory, and even a reloading components inventory.