Drive films. And characters, like everything else film, need to take on a sense of reality for a reader visually — but also emotionally. Because of the amount of time new film writers spend getting it pounded into them everything on the page has to be visual and filmable, however, that emotional element often gets lost or just deleted. And too often character introductions simply become a name, an age, and a description of what a character is wearing. Which reads something like “BOB  enters the room. He is wearing blue jeans and a sweatshirt and is very handsome.” Or, “Megan  enters the room. She is a natural beauty and wears a crisp white blouse and a black skirt.”
The problem with those introductions is, a reader learns absolutely nothing about WHO the characters are. All a reader knows, reading those descriptions, is what characters are wearing and the characters’ approximate ages and that the characters are generically attractive.
The assumption made by writers writing those types of character introductions is that a reader will get to know the character by following his or her actions during the course of the story. [This is pretty optimistic because lots of readers, if the character's introduction is boring and uninteresting, are not going to stick with the character that long.] But the above descriptions do not not address the actual goal of a character introduction. That goal is, literally, to introduce a reader to the character. And in that introduction you want the reader to get an impression of who the character is as a person. That is where authorial intrusion comes in.
[Everyone knows what authorial intrusion is right? Just to be sure, authorial intrusion is when a writer breaks the story wall and addresses the reader directly with statements coming from the writer clearly directed at the reader. For example, if you are reading a script and the scene description says, literally, "Okay readers pay attention this is a big clue and is going to be important later"? That is authorial intrusion. And, likewise, if a character introduction says, This guy used to have it all, now he's got nothing left but lint in his pockets and a hole in his socks? That is information that could only be coming from the writer and going to the reader. It is not something you would see on the screen. Which is also authorial intrusion.]
Character introductions are the one time in film writing when you get to really run with authorial intrusion and say something about a character that is an observation you, the writer, are making about the personality and internal make up of the character. This observation does not have to be filmable. This is an observation that is purely internal and coming straight from you the author and telling the reader about who this character is. This is the first time the reader meets the character, and, just as people meeting each other for the first time will evaluate the other person based on a first impression that is based on appearance but also on an emotional response? A reader will base his or her interpretation of a character on this first introduction on both a visual level as well as an emotional level based solely on the character’s introduction and what you, the writer, tell the reader about this character when he or she is introduced.
So. This is the one time you drop all the rules about only writing what can be filmed and run with authorial intrusion. Because you want this first impression to be big and have impact on the reader. Especially when you are introducing a lead. It has to count. And, this one introduction will color every interpretation of later actions and behavior. Because your job is not only to build character through actions or dialogue here. Your job is to “set” the character in the reader’s mind so she or he may interpret action and dialogue in the context of who this character is.
This is where the thinking process that goes “the reader will learn about my character through the course of events” goes wrong. This is just not true. The reader learns about the character through the introduction, and then interprets all following events using that original first impression, the character introduction, as the measure of everything to come. Take that away and try to make the reader just stick with an undefined character to find out what might be interesting? It does not go so well. Because, you did not do your first job. And that was, introduce the character to the reader.
*Excerpted from the lecture “Authorial Intrusion is Your Friend” from the lecture series “Character Writing,” Max Adams, AFW