Rotten Tomatoes - Rotten Tomatoes is a review aggregator, much like IMDB, where you can find commonly held opinions on movies by reading popular reviews. In addition, this site is also useful for finding information about upcoming films and film news.
Society for Cinema and Media Studies - The SCMS is a great tool for finding any sort of scholarly source for film critique or analysis. With the journal database, you have access to a myriad of different film magazines and databases.
Academia.edu - Much like the SCMS, Academia is a great place to check out up-to-date scholarly film critique and analysis. An account is required.
Timelapse.com Media Magazines - Timelapse.com has a great list of magazines that deal with film and film topics. If you're ever in the need of an article on a film technique or a film style, this is the place to go.
A trope, or at least the kind of trope used in the context of "the fish out of water trope", is any sort of rhetorical or story device used in fiction. TV Tropes is a website dedicated to cataloguing these tropes in an easy to use Wikipedia-like format. It is an amazing resource for anyone looking to create or analyze a work of fiction, film or otherwise.
Writing about film is unlike discussing any other form of media, because of how influential movies have become to the American landscape. There's no more popular American pastime than heading to the movie theater with a bucket of buttered popcorn. If you've ever wanted to make your opinion known on a film, you're on your first steps to becoming an accomplished film critic. But, you aren't there yet. There are a lot of things you have to learn before you can properly assess a film in its proper contexts.
And also, of course, there are more than just reviews when it comes to film analysis. There are critical essays, screening reports, and theoretical essays as well, each of which fills a particular niche within the scope of film analysis.
In order to properly assess a film, you need to learn about all the elements that go into making a film. This website does a good job of outlining the five formal qualities of film in an easy to read manner. Read up, because if you want to present your opinion and have it be accepted, you need to be well-informed.
Just writing about a film can help you understand a film. When an audience watches a film with a critical eye, asking why each element is in the place it is in, it's different from watching a movie normally. It's still just as engrossing, but now you're using your mind instead of just your eyes.
If you're interested in further reading, please check out Timothy Corrigan's A Short Guide to Writing About Film, an invaluable resource to anyone who wants to learn more about writing about film.