Remember - you've only got 15 seconds, and you want to be sure to say what you want to say, as clearly as possible.

Avoid camera shake, consider your lighting (hint - more is probably better than less), and get the action in fast. If the situation allows it, you might also consider more than one take - it'll make your editing easier when you get to your computer. Shoot a bit before and a bit after the scene you're shooting - you'll want a few frames to allow for transitions.

Play with the framing a bit - try and keep your recording memorable - just don't make it memorable for the wrong reasons!

When your films recorded, that's when the inside work starts.

If you've filmed on an analogue device, the getting the recording over to your machine is up to you - sorry! If you've gone digital, then refer to your device's manual - it's generally pretty simple.

If you're on Windows, then you'll be looking for something like Windows Movie Maker. On Mac, you'll want iMovie.

If you're more than a casual user, you'll probably have something in a more professional vein - if that's the case, you probably don't need anything I've got to say on the subject - just go to it, and use your expert knowledge.

The rest of you, read on.

Get all your clips imported - and rough out the order you want them in - this will give you your first rough cut. You should be somewhere near the 15-20 second mark, but don't matter if you're a few seconds either side - we'll get to that bit.

Make a backup copy. Call me paranoid.

One of the great things about Moviemaker and iMovie is that they offer all these nifty little tools for transitions between scenes. In the interests of simplicity, either pick your favorite, or the one that you think fits the subject matter the best, and stick with it. Again, remember you've only got 15 seconds, so don't pick one that takes 5 seconds to complete.

Add in your titles - again, being mindful of the time constraints. There's no point in having 50 words on the screen, people won't get time to read it.

Now you've got the structure, the content, and, if you're anything like me, about 25 seconds of content.

Make another backup copy. Call me paranoid again.

Next comes the hard part - trimming down to meet the time constraints. Again, if you're like me, you'll end up agonizing over the last few frames, but it's got to be done. Now, cut out all the fat, all the dead wood, every word, transition, every frame that doesn't add to your message.

You're done! Its 15 seconds! It says everything you want it to say! It's a masterpiece of brevity and content.