How to make a documentary
To make a good solid documentary, one has to denote then add connotation to the subject matter.
Pre-Production: The ways you go on deciding what you should make your documentary about. Well for instance, the drama of a piece can be developed by starting in a small personlised setting, and having the story have an overreaching arc.
You could take something as simple as a man building bicycles, which turns out he's making them for immigrants who are homeless, leading into filming the National Front and leading it into a piece which fulfills a bigger picture.
The most important thing is always personlisation, which allows the audience to connect with the piece of film they're watching. You would never throw them statistics or numbers. This is why all good documentaries make estimations. You would instead quantify those into something else. Let's say, "they were more than 25,000 people at the festival, enough to fill up to two football fields" You may never have been to a football stadium before, but you've seen it on TV. This allows the viewer to gain an understanding of the amount in visual terms.
You should never ever make the audience feel stupid. An iconic landmark, the Eiffel Tower for instance, does not need an explanation of being in Paris, France. And definitely don't add a caption. The audience will automatically say "duh", instantly switching off in annoyance. Instead, tell the viewer something interesting about the Eiffel Tower - like how many suicides happen per year; or that there's a party in France that wants to tear the landmark down.
An opening image could be as simple as adding a caption to set the stage, so to speak - like "Glastonbury 2014". You'd instantly know where you are in the world. And it's then, with the opening narration/dialogue, that leads it quickly to its subject matter.
However one has to be careful of the authoritarian aspect of the voice over - and being careful not to belittle your audiences intelligence; as you should be aiming for the intelligent audience, who aren't knowledgeable about the subject matter.
For instance, "at Glastonbury, over 40 people are arrested for drugs." Or you could say, "this is the biggest music festival in the world. As you can see, this tangent leads to the subject matter without any hesitation.
When filming a documentary, the moments one needs to capture are the organic pieces, where you see those in their natural elements; as in if you making a documentary about the homeless, you would show the man/woman sitting as masses of people walk passed.
Documentaries are still a piece of drama, and to sustain the viewers interest, you will have to push forward with your subject matter with the visual imagery. Making it interesting and having it stay relevant, that should be the intention for the shooting of the film.
To actually find and converse with the subjects, having a tripod makes a huge difference, as the general public will assume you're professionals making a film. One this point, getting permissions from the local councils and/or the relevant festivals or places is critical. There's nothing worse then being unable to have a day of filming.
Editing: In terms of post, there are a 100 different styles but always keep it relevant to your subject matter. Don't instead decide to make a piece that's akin to the hard to understand art-house cinema. The audience will have a hard enough time watching the visual imagery, and having information told to them.
Over-extending your input could cause cogitative dissonance, and the viewer will switch off. Always take care to keep that in mind.Never tell your viewer the information, always try to show then explain.
A finished documentary should be a factual piece of information that simplifies an entire subject matter, allowing an audience to simply understand without any prior knowledge beforehand.