Writing about film and other forms of media I consume is a very deep passion of mine (no duh). There's no shortage of people on the internet writing about films, games, comic books, etc, to the point where it can be overwhelming sometimes. Who do you watch? Why do you watch them? What does this person offer that others don't?
It can be hard to stand out in the sea of content creators that is the internet. I know I struggle to this day to make my writing more nuanced and complex. These are just some tips I've learned to over the years that helped improve the quality of my writing and I hope will inspire others to do the same.
First, you should at least have a basic understanding of technical qualities in film such as framing, dialog, lighting, acting, cinematography, sound quality and effects. You don't have to have actually had jobs in these fields, but if you wish to comment on the technical aspects of a film, you should at least have some understanding of what makes a shot look good and what makes a shot look bad.
Second, you should then add onto the technical knowledge with artistic knowledge such as themes, ideas, messages, emotions, character motivation and character arcs. What is a film trying to say with this dialog? What emotions are conveyed with this character in a wide shot? What motivated a character to do that? The technical aspects teach you the "hows" of film making, these aspects teach you the "whys."
I find this to be the more interesting of the two aspects, because understanding why a person or people made a film and what emotions/themes they wanted to convey is what gives art its purpose. These are the qualities that make film fascinating to talk about and allows them to be windows into a certain person's psyche, or the ideas and beliefs of the culture/society/times that the film was made in.
This brings me to my third point. You should have some understanding of the culture and times a film was made in. Films are not made in a vacuum, they are the products of specific cultures and times. These are the same cultures and times that influence the beliefs and ideas of the people who live within it, such as filmmakers.
This illuminates the themes and messages of any given film, and helps add important historical context to a film. Why was "Star Wars" such a smash hit in post-Vietnam War America? Why did a film like "The Avengers" connect with audiences the way it did? Why was a film like "Black Panther" seen as a cultural milestone in 2018? These are the questions you should ask when writing about the historical and cultural significance of film or any form of art for that matter.
Most film reviews/videos I see on places like YouTube usually only do basic technical evaluation with some surface level discussion on themes and character. Most typically lack the cultural and historical context analysis. Evaluating aspects of the culture a film was made in can shine light on what a film is trying to say and vice versa. It can also act as a window into a culture that isn't your own.
It helps to learn basic aspects about other cultures when viewing foreign films. One of my favorite classes in college was Asian Cinema. Not only did I get to view a wide variety of genres (Kung Fu films, Korean Drama, Noodle Westerns) from a wide variety of countries, but I was also taught about the unique culture of each country and why they made some of the interesting choices in their films. This helped my writing a lot and expanded my worldly knowledge.
That's what's great about writing and reading about film; it's all of the new and interesting things you can learn from a deeper analysis. These are the fundamentals of film analysis and they give us a better understanding of art. Understanding them allows you to understand the art you love to a better degree and allows you to write more in depth opinions and essays about the art you love discussing with others.