A fellow wants me to look at his script that is based on a true story about himself, with himself as the main character.
Although the impulse to write about yourself can be strong, I recommend you suppress it, at least until you've written a bunch of screenplays.
It is very hard to write about yourself. To you, you are obviously an important and compelling character. But in a screenplay, you have to make us care about the main character, you can't take it for granted. It's much harder to remember that when it's about you.
When yo're writing about yourself, it's hard to give yourself interesting flaws. We all like to think that we're good, nice, kind people. Good, nice and kind are not dramatic traits in a movie. You will be tempted to give yourself an above average sense of humor. But humor tends to deflate whatever is going on. (Partly why the line "just kidding" is so annoying wherever it crops up in a screenplay.) You will not want yourself to make dumb or foolish or reckless decisions; but characters need to.
You don't have a story. You have a life. A life is not a story. A life is a mixture of many stories. It is harder to separate yourself from your own life; whereas if you are telling a story about something else, it's easy to identify and delete the events and characters that don't belong to the story.
When you write about yourself, it is extremely hard to remember that the you in the screenplay is not you
, it' s a character with your name
. And that character has, and needs to have, a life of his own.
Most importantly, when you're deciding to write a story of your life, it is very hard to evaluate the question "why do we care?" Obviously you care about what goes on in your life. But, though I am sure you are a good and kind and nice person with an above average sense of humor ... we probably don't.