The thread lives! Again!
Keep a pen and a notebook or some paper close to hand at all times, you never know when you'll need it. Last night I was just lying in bed half asleep when BAM-the Plot I had been needing for months appeared. Out of nowhere. If I hadn't had a notebook on the bedside table that miraculous plot might have been lost for ever. Like I said, you never know when you'll need one.
And characters. They don't need to be people you know, you'll be surprised where they can come from. One of my favourites is my Morrowind char who I've transfered to my world(not the plot of the game and what role she plays in it, just her attitute and personality). I spent time playing as her, and as a result of going through so many experiances with her, I know her inside out and top to bottom. I know what sends her into a sulk and I know what sends her skpping down the street. Know your characters, if you don't know exactly what they'd do in a situation, you can't expect to be able to tell your readers. Talk to your characters, think about what they would do if they walked down a street, if someone asked them a question, what would they say back, heck, take them to the pub if they're that kind of person! (obviously you should do these things mentaly, you'll get some funny looks if you walk down a street staring into space or talking to someone who isn't there
).