How to Review a Film
What's in a review?
Good reviews always have some component of analysis. The critic's personal opinion plays a big part in this form of article, and the analysis comes from not the fact that something is good or bad, but why it's good or bad. If you think "Batman v. Superman" is atrocious, simply stating so won't get you very far. Why is is that way?
Reviews also tend to have some element of summary in them, to ground the audience. A total stranger should be able to walk into your review and know what type of movie you just watched, who are the main characters, and what is their struggle, before skimming over what elements of the film did/did not work.
This is hard to do, for even experienced writers. Because film has so many elements to it (directing, photography, acting, etc.), some of which might not be worth explaining in further detail, it is your job to pick out what's important in the film, and explain why it's important in descending order of important. In journalism, we call this the inverted pyramid.
Not all elements of the film should be talked about in equal proportions, and this makes articulating yourself a precarious balancing act of what elements made the most impression on you.
Even if you hate a film, there are ways to appreciate it for what it is. To do so, you must remove your personal prejudices from the genre you're talking about and judge the film by its own standards, as established by codes and conventions of likewise films.
Journalism is never unbiased, but your job as a reviewer is to break down the film into its basic elements to see what works, what doesn't, and most importantly, to see if each elements works well in conjunction with each other to make a pleasurable whole.
It is important to base your criticism off of units of analysis, such as genre conventions and the language of cinematography, as there are absolute ways of shooting a good film, and making a film that works for the specific genre it belongs to. Individual scenes from the movie serve as your evidence that you can put into contrast with other films in the genre.
Be brutal only when necessary, as you will receive a backlash for being necessarily harsh towards a particular film. You might even lose your ethos (credibility) if your criticism gains a reputation for being unreasonable.
Communicate your passion
If you chose to review film regularly, you obviously love it. Don't let your love blind you, but let it direct you. If a piece of cinema pleases you, analyze that pleasure and tell us why it pleases you. It just might please someone else in the same way.