Hi,
I've learned this from working on my first short, which has completely changed story ideas three times. When you say "short", I presume that includes everything from modeling and texturing to sound effects and music.
First, keep it simple, one or two characters at the most. Also limit your locations to one or two areas.
Going in, have a clear idea of what is happening in the short. Just as you would for a feature length film, storyboard from start to finish. The storyboards don't have to be works of art, they could be stick figures or whatever, as long as the camera location and movement and the actions within the scene are clear to you.
Be patient with yourself. Know that animation takes time, maybe longer than you realize.
Be persistent.
Be organized. What I've done is created a folder for my short. In that folder, I've created several folders for models, textures, etc... And in all the projects that I've done, I've saved everything externally into those folders.
Initially, it's best to do each shot as a separate project file. Each project file should have only one choreography, this helps keep things uncluttered because you have only the files you're working with for that choreography. Later, if you need to, you can combine projects easily by simply bringing in the other choreographies.
Take the time to really LEARN from what you're doing. Take the short all the way to final render.
Don't use the beta versions if you're on a deadline.
Good luck with it, if you need help as you're working on it, this forum's the best place to turn. And SHOW IT OFF when you're done.
Just my two cents,
Steve P.