Critically examine some professional examples  You can find some examples here:

Becker
Wacquant
Bourdieu
SOSIG archive ( huge list of examples)

If your library has access try the journal Ethnography

See also the nice multimedia RLO on participant observation produced by UCEL

List and discuss the techniques:

what did the researchers actually do?
how did they gain access to the people they wanted to study?
what problems did they encounter?
how did the researchers participate unobtrusively yet remain ‘objective’?
how successful do you think they had been?
what preparation do you think you would need to use this research technique?