What is film criticism? And what would you criticize in a film? and what would you criticise in a film

You can use
the same criteria for a novel, play or short story and apply it when evaluating a film. Such
aspects as setting, characters, plot or intrigue, symbolism and themes all need to be
considered.

As mentioned in the previous comment, a basic knowledge of
film-making and film jargon (terms) is needed as well. This is especially true when considering
the way a scene is shot (for example, a close range as opposed to a stock shot) and the manner
in which it is "set" into the rest of the fillm. Is a scene suddenly there or does it
fade or in or out?

A good source of study is Gore Vidal's television play
"Visit to a Small Planet" in the MacMillan edition Insights into Literature
since a glossary of such terms is provided.