This year Apple is again running a film festival for high school and college filmmakers -- the idea is to make a film basically from scratch in 24 hours.
Thinking of participating? Check out John August's top ten tips for making a short film in a limited amount of time. My favorite: "Protein, not carbs. Because you’ll likely be working all night, sugar will send you into a crash."
Of course, the most practical is to "Go funny." This applies to documentaries as well as narrative films; if you can display a sense of humor towards your subject -- however dire -- your film is much more likely to be remembered and rewarded.
Best of luck to the participants.