I always make a save game as soon as the game LETS me, and then ~never~ touch that savegame. I can always start a "new" game at that point (usually before you finalize your character, so you can change name/appearance/stats and so on).
After that sacred un-touchable save, I'll usually make saves before important junctions in the story, although I almost never go BACK to them, if I am honest with myself --- going that far back in the story, I always forget what I did, when, and in which "iteration" of the game. But by the same token, it is nice to have a few "old" backups in case something drastic happens to the two or three "live" saves that you cycle among. The Autosaves are just gravy, pretty much only used when something bugs out or if, eg, I get stuck at the bottom of a vault and can't find my way out I can just say "Screw it" and reload the save before I entered.
The savegames usually have a picture taken when you make the save, and the date/time stamp but unless you manually do a /savegame command from the Console, I think it just labels them numerically (Save 004 and so on), with the zone you're in, perhaps. I much prefer being able to name our own games (without using console commands) so that I can name a savegame as, "Pre-settlement-start" so that I know I can roll back to that point if I start building my settlement and get screwed up and mis-managed and just want to start a clean slate without the wasted resources I spent while tinkering. If I have to remember that Save 034 was the savegame that I need to load, it would be harder to do.