Before beginning a search for film reviews, it helps to know the film's release date. Internet Movie Database is a good source for this kind of information.
Film reviews are usually published in popular magazines and newspapers, and you can find them in the same places you find other kinds of newspaper and magazine articles. See above for information on finding newspaper articles. Below are some other sources that you might find useful in searching for film reviews.
Academic Search Complete. Covers recent 2 decades of popular magazines.
Readers' Guide Retrospective. Covers popular magazines from 1890-1982. Search for the film title and the phrase "film reviews." For example, "Shakespeare Wallah" and "film reviews".
Film Review Index. Covers magazines, journals, and books from 1882-1985.
Variety Film Reviews. Reprints Variety film reviews from 1907-1996.
Film Review Annual. Yearly digest of important reviews. Covers 1981-2002.
The New York Times Film Reviews. Biannual compilation. Covers 1913-2000. Basically superceded by the Historical New York Times (part of ProQuest Historical Newspapers--see above).