Interviews and presenters
Nowadays camcorders are used for more than just filming home movies. A large community of amateur videographers now film short clips to put on web sites such as Google video, You Tube and their own personal sites. Some of these are purely for entertainment while others are for information purposes e.g. local history societies interview people for their memories of the locality.
The quality of modern camcorders and computer based editing systems combined can produce excellent visual results which are often let down by poor quality sound. The main reason for this is that the built-in video microphone is usually too far away from the people being filmed.
At the time of filming, our ears, eyes and brain work together to effectively suppress the reverberation and other unwanted sound sources in the room to allow us to hear what someone is saying, what we hear is different to what a microphone hears.
This is where external microphones are required, the closer a microphone can get to the subject, the quieter other unwanted sounds effectively become.
If at this stage you dont have any external microphones then the best advice...