Some of your interviews will be in-depth sit-down sessions, while others will be less formal.

Before launching into how to shoot an interview, be sure about the style of interview you have planned. First of all, will you include the interviewer's questions in the final presentation? If not, make sure interviewees know this, and prompt them to include the questions in the answers. Otherwise you'll end up with out-of-context and unusable one- or two-word answers like this:

Q: For how many years have you been managing this project?
A: Fifteen.

Don't set yourself up for "yes" or "no" answers. Ask people open-ended questions; have them tell you stories about what happened. If an answer is too general, ask for examples. Ask people to describe and explain things, events and feelings. "What was that like?"

There are many ways to do a documentary interview. Here are three:

• In-depth sit-down interview
• The "walk-and-talk"
• Streeters

An in-depth personal interview with a main character can carry an entire documentary, as the interviewer peels back layers of the subject's life and times. A good way to approach this kind of interview is to ask your questions chronologically: "And then what happened?" Interviews with secondary characters can be in-depth as well, but they tend to be factual, as the interviewee provides context and background: "Please give us a sense of what it was like politically at that time."

The key to in-depth interviews is to listen. Maintain eye contact with your subject, and don't look down at your notes and questions. Move the interview forward by responding to what your subject is talking about rather than waiting, poised to ask your next question. Have a conversation with the interviewee. Don't let opportunities to explore emotion slip away, and don't settle for generalizations. If a subject says, "That was the worst time of my life," you need to follow up with something like, "Tell me why," or "Please talk about that."

Interviewing a subject while they are doing something can be engaging for the audience and more relaxing for some interviewees than a formal sit-down. For example, in a factual interview, consider filming an athlete talking about the importance of pre-game warm-ups while she's doing her stretches, or, in a personal interview, have a single dad talk about his domestic challenges while he's preparing a meal for his kids. Then there's the literal walk-and-talk of a handheld interview where the cameraperson moves backwards trying to keep a uniform distance from the forward-moving subject.

Streeters or vox-pops - often known as man-on-the-street interviews in news shooting jargon - are where you park yourself with camera and microphone on a street corner, hoping somebody will stop and chat with you. These short informal interviews typically ask the same prepared questions of passersby to collect their opinions on a subject. Streeters make for short, snappy sound bites that can be cut into the doc to support (or contradict) its main themes.

The key to conducting a useful in-the-street interview is to put the subject at ease. Make it light, make it fun. Tell them what your doc is about, and ask if they would like to comment on the subject. Always give the last word to your interview subject: "Is there anything you'd like to add?"

Tip: Begin all interviews by having subjects introduce themselves on camera: full name, age and title or position, so you have that detail later for proper pronouncement during voiceovers and proper spelling for graphical IDs or even possible legal needs.