Interviews are a great documentation tool, whether interviewing artists about their process or colleagues about the work they do to maintain artworks under their purview. Interviews also help build the historical reference for the field of conservation, to understand how materials and techniques evolve, especially with contemporary artworks.
When interviewing there are so many simple things you can do to ensure you get a great looking video while using the most inexpensive of materials, as listed in the equipment section. For specific tips about the different equipment set ups you can work with have a look at the equipment specific tutorials.
The most important part of good video is sound. So always take the time to find a quiet location, you may need to close some doors, turn off fans, machines and especially refridgerators to reduce background sound. Moving away from noisy devices also helps. If you have trouble noticing all these background sounds test recordings are great to find out what sounds you might not be tuning into that are distracting. Always check your subject's microphone sound by using headphones, and continue to monitor the sound quality throughout your interview.
Don't set the headphones aside once the interview starts, this will prevent you from knowing if you microphone battery has run out or if you are getting other audio problems that arise mid-interview.
Firstly, your camera should always be on a tripod or similar stabilizing device, you don’t want camera movement to distract the viewer from the subject and what they are saying. Consider the lighting and setting, outside light mixed with indoors creates poor color, try all one or all the other for better color on your subject, for instance draw the blinds and turn on more lights indoors. All that said more light is always better, your subjects will feel more comfortable if you are not documenting them with a shortage of light as that tends to create unflattering shadows. You can simply set up a worklight over your shoulder pointed at the interviewee.
Keep your subject on topic and don’t be afraid to ask them to state ideas more clearly a second time, you can cut out parts that are repetitive if you are using editing software. If you don't plan to edit you can also stop recording and start your camera again so that you can quickly patch the good clips together using the youtube editor. You can also have them answer your questions a second time while being more concise, a round of practice sometimes helps your subject to organize their thoughts. Make sure you have a list of questions and/or talking points to work off of while you are interviewing.
Also make sure you stay seated in the same spot on eye level with the camera so that your interviewee is not looking far off up or down out of the frame.