Along with demonstrating your mad writing skillz, the first ten pages of your script should clearly establish who the protagonist is and what environment he has chosen for himself. One of the key elements of the protagonist’s environment is his job and there are two important goals that you can accomplish by giving your protagonist the right job: 1) Demonstrating his skillset (or “skillzset,” if you prefer my previous spelling); 2) Showing how he avoids confronting his internal flaw.
Let’s start with the flaw. Every protagonist should have an internal flaw that makes his life significantly less enjoyable than it otherwise could be, and which also makes his external goal particularly difficult for him to accomplish. That internal flaw should be so painful for the protagonist to deal with, that he has had to find an environment (including a job) that allows him to avoid encountering it. For example, someone with a fear of heights would probably not work as a window washer or suspension bridge construction worker. He would find a job that allows him to remain as close to the ground as possible at all times. Your protagonist should do the same thing.
In addition to letting your protagonist avoid confronting his internal flaw, a well-chosen job will also demonstrate a particular ability that the protagonist can use to overcome his antagonist. In Hitchcock’s movie “Rear Window,” Jimmy Stewart’s character is a photographer, so he uses one of his bright strobes to blind Raymond Burr in their final confrontation. In “Slumdog Millionaire,” Jamal’s profession as a tea server for telemarketers allows him to avoid both the life of crime that his brother has chosen, but also his own inability to rise above his social caste by placing him at the absolute bottom of the corporate ladder. However, this job also demonstrates Jamal's clever resourcefulness by showing how he takes full advantage of those rare moments when he is asked to cover for a telemarketer who needs to go on break. Jamal not only uses these opportunities to contact Latika, but also to get a spot on the “Millionaire” show.
I should throw in the big ol’ caveat here that most protagonists, even in highly successful movies, don’t have a job that both demonstrates their unique abilities and allows them to avoid confronting their internal flaws. But most good screenplays do give the protagonist a job that has a direct influence on the story, so at a bare minimum, you should make sure that yours does too. However, it's so efficient way to manage those two character traits this way that you could set yourself apart by giving your protagonist a job like this. Give it a shot and see if it improves your story.