The best lecture on writing I ever heard may have well been the shortest. 

The professor suggested to get over a hump, pretend you've just called your best friend with a juicy piece of news, and start the conversation with "Guess what?"

 

From there the story will follow a natural progression: the most interesting stuff at the head, with a natural unfolding of detail, ending with a bring-it-on-home kicker.

 

Don't sit there staring at the monitor. Phone a friend!