Keeping track of it all...

[CyCo]

Firstly, check out the Character Sheet thread that is stickied here in the GM Forum, you should find a NPC sheet, with from memory is about the size of a index card.

Then when you make up a NPC, boil it all down to fit on the NPC sheet. Try and condense the dice rolls. When players make up their characters, take it off them 'for research into their characters', and make an 'alter ego' based off their characters. Will give you some extra NPCs without doing the hard work. If your characters start interacting with the 'barman' who was just a piece of scenery, start up a NPC card for him as well. Just flesh him out as you go, only try sticking to a OCC if you really feel the need to.

After a while, you should develop quite a stock of NPCs.

As for subplots and sidetrips, your nearest source is your favourate news site. A news articled about a bank heist can easily be translated into most settings. Scan the news articles and build from them like building blocks. Adding to the bank heist, you might see an article about a car chase, a foiled terrorist attack, and a wealthy investor.

That becomes a story of a bank heist that is going to finance a terrorist attack. The wealthy investor might be the one who is behind the 'terrorist' attack, who doesn't want any leads heading back to him (thus using stolen monies). And the car chase, well, that's obligatory in an action movie, right?

Which is a nice segues, for movies are another great source for plots, characters, settings, ect. And for that matter, so are novels, cartoons, tv series, comics....

Indeed there is a plethora of ways to grab an idea that someone has already thought up, just ready for the plucking.

8p

[Kelorin]

In addition to Cyco's suggestions, I recommend having a stock of pre-generated stats, and a separate list of generic or stock 'extras'. For non-combat NPC's like shopkeepers, barmaids, random citizens, the town mayor, planetary governor, etc. all you really need is name, age, sex, alignment, and general disposition. If the characters are not going to get into a fight with the NPC, full combat stats are unnecessary, beyond a few notable attributes, like the barmaid is really hawt (P.B. 21), the ship's engineer is really smart (I.Q. 19) etc. If push comes to shove, match up the NPC with some of the pre-generated combat stats you've already got a library of, and a way you go.

Make full use of pre-generated NPC's in the books. Maybe your PC's aren't going anywhere near the Siege on Tolkeen. Change a few names and key stats, and the NPC's from that storyline are ready to do double-duty in your campaign.

Another suggestion for generating character names in a hurry. Try Seventh Sanctum: http://www.seventhsanctum.com/

For side quests, I always try to think of 'other things' that happen to be occuring in town 'X' or planet 'Y' in addition to whatever the main thing the PC's are doing there, and how some of the stock NPC's feel about those events. Knowing some of these details, can allow the PC's to get involved in local intrigue without necessarily having fully fleshed out adventures, or again make full use of pre-published Hook, Line and Sinkers. If necessary, change details to make an existing HLS adventure fit wherever your PC's are at the time.

[lather]

NPCs can be found in some of the books.
You may need to make minor alterations, but, as was mentioned, these are easier than starting from scratch.