Producer, P. [Screen name]. (Full date of publication Year, Month Day). Title of YouTube video [Video file]. Retrieval information
Example—reference list entry
Apsolon, M. [markapsolon]. (2011, September 9). The haunting tape 14 (ghost caught on video) [Video file]. Retrieved from http://www.youtube.com/watch?v=6nyGCbxD848
Example—in-text citation
Apsolon (2011) shows ...
or
… (Apsolon, 2011, 6:04).
(If quoting/paraphrasing from a video clip, it is useful to put the time that your quote/reference appears.)