I know... I know... Handwavery is the answer... but I still spend too much time involved in "making things reasonable and logical".

Currently, I'm working out backstories for a larger freighter crew (about 20 or so) and after figuring a bit, and writing down a few things, I am back to building a timeline so I can keep everything straight. I don't mind inventing things on the fly during a game, but when I'm planning things out, I can't seem to stay away from the time sinks involved with keeping everything organized.

This may just be mental diversionary tactics like I experienced in college... anything that could interrupt study probably would. I was also a chief instigator of shenanigans, so I guess it is fair to say I trained myself that way. I can certainly still do one-off stories easily, but the planning stages seem to get more and more detail.

Of course, my players made me this way a bit as well. Derail experts they are. Non-linear thinkers and problem solvers. In the end, maybe it is justified, right?I doubt I'm alone in this, but is there a cure for this or do you just trudge on through the details and eventually have an amazing encyclopedia of trivial information just in case you need it?

I tend to use sketches that I fill in as needed. There's a 5 word NPC building guide floating around on the interwebz somewhere. Basically, just pick a few interesting adjectives and an anecdote or two and that's your NPC. If someone asks for more details, that's when you can start filling in the blanks, but only do so when you need to. Remember, if you didn't tell the PCs something yet, it doesn't exist. Also remember to let the PCs do most of the work when coming up with backstory. If they jump to a conclusion that you didn't think of (and it's neat and/or amusing), feel free to latch onto it and incorporate it into the larger world.

Oh yeah, the PCs are totally on their own. This is something completely different. I have names and was working on the two-three characteristics. I use that all the time. But then I started to try and get a feel for them a bit and how old that many people would be and the differences there. And suddenly I was in full-detail mode. Not always bad, but I'm not writing story at that point, I'm just adding in details. I guess it worked for Tolkien... lol... if someone ever finds my notes in 50 years... lol

Oh, I meant let the PCs come up with backstories, plots, subterfuges and conspiracies that exist between and among your NPCs. Why should you do all the work?

There will be chances for that. Why do I do all that extra work? Usually for the element of surprise...

Not all surprises are bad ones. I try to mix it up and apply creative juices to all of it. Sure, I let them interact with my creations, but I want to build a web to trap them in as well...

Many times in my GMing past the players will jump to conclusions about NPCs that become "real" simply because it was more fun than what I had originally thought of. The players work in my game, and they often don't even know it.

This sort of sandbox gaming is what I tend to run. I prepared myself at first by building my knowledge of the setting - a daunting task to say the least. Then I borrowed or created set pieces to cover any number of situations. How many cantinas does one group really need? One with some reskinning. Same goes for NPCs. I always keep a list of names and species handy as well.

Now I have the bits and pieces to keep on truckin' in almost every situation. It's a sisyphean task to know everything about this particular setting, but if you have the right tools at hand you can wing it with near impunity.