The first thing to do is to have a look at a few films, bearing in mind how ideas are conveyed. Look at shorter mediums such as advertisements, cartoons and pop videos for examples of how things are done in a very short space of time. The audience will have to have some empathy with characters in the film, and you'll have only a short time to win that empathy.

The idea for the script should be strong. Let the ideas flow in the beginning, but get down to practicalities soon enough and think about what is feasible. Think of the strengths of film and the sort of things that can be done so well with film, like bouncing back and forth in time and place - or car chases. Equally, think of what film can't do so well, such as convey the interior world of a character in the way that one short sentence in a novel might.

The key to film is show, don't tell. But good dialogue is essential: read it allowed in the classroom and decide if it sounds good - i.e., sounds like what you really do say on a daily basis. A few people standing in a room talking to each other for ages is a waste of film. Film is all about movement - get as much of that in as you can. Tell the story visually in a sequence of pictures. Moving pictures - yeah, movies . . .

Discuss a couple of the worst films you ever saw, and decide what it was that made each so particularly crap - then avoid repetition.

Think about the size of the story you can realistically tell in such a short space of time. Scripts are broken up into scenes. As a rule of thumb, one page is about one minute long. But you need to read it to be sure, and to time stuff like "all hell breaks loose" - for how long? Be practical: "for five minutes" may be the case in the real world - but that's a good half of your film. You might lose your audience.

Think about the style of film you all most enjoy - comedy, science fiction, thriller, period drama? Or would you prefer to make a documentary?

Don't be nervous; making something in science fiction mode, for instance, isn't as hard as it might seem - lots of tin foil and silver makeup worked perfectly for decades.

Don't let the film peter out and hope for the best. A good ending is crucial - in fact, scriptwriters often think of an end first, and the rest of the story arises out of how to get to there.

Without realising it, people have a very sophisticated understanding of the language of film and can get ahead of you very fast - and get bored. Think of something they wont necessarily expect. Well, there'll always be some smarty-pants who gets there first - but forget about them, they're too boring to worry about.

Special thanks to Hugh Linehan, Irish Times film critic and short film maker extraordinaire