REMEMBER - usually, your pre-production is actually being assessed. So present it well and make sure it makes sense!
REMEMBER#2 - Before you do all of this, you need an idea that is worth making. Mindmaps and brainstorms and conversations with your team are vital. Generate a LOT of ideas, not just one - your first (and second, and third) ideas are the same as everyone else's!
PRODUCTION SCHEDULE - It's just a (shared) calendar. Make deadlines for each stage of the process. Each person should know what they are working on and when it is due. Basic requirements are deadlines for pre-production, production, rough cut and final cut.
STORYBOARD - This is important. A visual plan of your key shots. It should show the distance and angle of the shot, any camera or actor movement, possibly give ideas about colour and light, and suggest links between shot and sound. See here for a bit of help!
SCREENPLAY - Perhaps the most important document of all, if you're making a scripted piece. Write a treatment first - a short summary of the plot. For a short film, one side of A4 is more than enough. George Lucas' original treatment for "The Star Wars" is about 11 pages long - we don't need that much.
Make sure everyone in your group is happy with the treatment BEFORE writing the screenplay.
MARK UP THE STORYBOARD AND SCREENPLAY - Everyone in the group needs to engage with these documents. It is normal to go through the screenplay in particular and annotate it from the points of view of cinematography, editing and so on. See here for advice:
LOCATION SCOUTING -Unless you are filming in the studio, you need to go to the place you want to film in, at the time of day you want to film, and check that it is ok. That means - is the light ok? Is there room to move? Are there places to recharge cameras if necessary? Can your crew and actors get food and water? What is the sound like? Bring your storyboard, try to capture a few of your shots, record some sound. More tips here.
SHOT LIST - Some people use these, some don't. Storyboards can be time-consuming and often cinematographers are going to focus only on more elaborate shots. Editors in particular need to make sure that they have enough footage for coverage, so sometimes what appears to be one shot on a storyboard (say, a two-shot for a conversation) actually needs breaking down into several shots (the two-shot and the two over-the-shoulder angles.) The shot list - basically, a list of ALL shots which need capturing, IN ORDER - can be more useful on set than a storyboard but it's not a replacement for it.