It is worth trying to catch as much speech as possible as it can be difficult to interpret out of context. Field notes can capture whispers and asides not picked up by a microphone. Avoid interruptions by putting a notice on the door that filming is in progress. After recording Time spent on careful labelling and logging of videos can save fruitless hours of searching later. As part of this process, organise a good cross-referencing system to other data.
Transcription is extremely labour intensive.
If notes of gesture and information other than speech are required or if transcribing group discussion allow up to 20 hours to transcribe each hour of video. The ratio is even higher if very detailed transcription is required but it isn't usually necessary to transcribe everything. Viewing the material and deciding which sections need transcription is adequate for some purposes. Always make back ups and use them for transcription and general viewing. Only use master tapes for producing edited versions.