I'm not a pro, but I have written several screenplays. I am currently adapting one of my mother's published novels into a screenplay. Screenplays and novels are different beasts. Some techniques that work in a novel don't work in a screenplay, and vice versa. For example, the opening scene in the novel I'm adapting is a girl sitting in the family kitchen worrying about the imminent visit of the mine owner and what bad news of many bad options he might be bringing. The reason she is focusing on the negative is the family has had a very difficult year. I can't film her thinking. Film can't look inside a characters head like text on a page can. I can add another person and have the two of them talking about everything she's thinking—very clunky writing. I could add a voice over narration—generally considered old fashioned. I could add scenes before the first scene and show the events that have her so worried. I could start with the mine owner's arrival and add dialog that reveals how anxious she was and why. Novel scenes and screenplay scenes rarely have a nice one-to-one association.
Screenplays are
short. It is usually impossible to cram every significant event of a novel into a screenplay. So you need to choose the most significant, the ones that drive the core story. The dialog scenes might seem like the most obvious to include in the screenplay version, but are they the most important?
I think outlining is more common among screenwriters than novelists. The space constraints in a screenplay are so tight. But there are certainly screenwriters that work without outlines. As for writing scenes and stitching them together, I know some screenwriters do that. I write scenes before I outline in order to explore how an idea would work on screen. I don't stitch these scenes together. They are just explorations. Bits and pieces might end up in final scenes.
Again, consider the extreme shortness of screenplays. Short novels are around 200 pages in paperback. Most of the novels on my shelves are 300 to 500 pages. Say your novel is 300 pages. A one page dialog scene is 1/300th of your novel. That same scene formatted for a screenplay will probably run two pages even after all the tags and interstitials are removed. That's two pages out of a typical 100 page screenplay. That same scene consumes six times as much space in your screenplay than it did in your novel. Is it important enough to justify that?
What is important to carry over from novel to screenplay are ideas contained in scenes. You won't have enough space for every idea, just the most important ones. Most scenes in your novel will include a mix of ideas that make the cut and that don't. The ideas that make the cut will probably be rearranged to have the most pleasing structure in the new form.
For example, say your novel includes a scene in which Mary and Jack search an office and find a letter that implicate Susan in the crime they are investigating. In the novel version, this scene reveals:
- Mary's policeman father taught her how to search a room and how to use a gun.
- Jack is a coward. This is important later when justifying why he betrays Mary.
- Susan is involved in the crime.
What if this is the only scene that takes place in this office? You might cut the location in the film version in favour of locations that host multiple scenes.
What if Susan is only a stepping stone to Harold and she doesn't know details about the crime? You might cut her character to save time.
So you cut the location, Susan, and the discovery of the letter that implicates her. You cut the scene. But there are still important character points about Mary and Jack that you want to keep. Put them in different scenes. That's what I mean when I say a dialogue scene you write for the novel is not necessarily a scene in the screenplay. Parts of it might be, and parts not.