Don’t put extra pressure on yourself unnecessarily. I once had a writing teacher who said, “Think of each page of your sitcom as being worth a thousand dollars. Then say to yourself, ‘is this page worth one thousand dollars?’” This teacher should be shot. First of all, his math is off. And secondly, there will be some pages worth five grand and others worth sixteen bucks because you’re just describing a character driving away to end the scene. Don’t put monetary values on pages or jokes or anything. It’s arbitrary and destructive.
Don’t feel every line has to be perfect before you can go on to the next. The end result will be a rather stilted very calculated script. Get a flow going. You can always go back and revise. Don’t let one difficult line completely stall the process. And here’s the dirty little secret: The lines won’t be perfect anyway.
Don’t clog up your pages with lots of stage direction. A reader sees a giant block of direction and best case scenario – just skips it, and worse case scenario – tosses the script away. Do the bare minimum and then cut that down.
Likewise, any big speech can be trimmed. Don’t fall in love with your rhetoric.
Characters rarely articulate just how they feel and exactly what they want. In fact, most people go out of their way to NOT express what they’re really thinking. They convey their feelings in behavior, innuendo, denial, misdirection, a smokescreen of humor – pretty much anything other than stating the obvious. It’s your job to find ways to get their feelings across in an artful not bald way.
Take the time to research and put your script in the correct format. This is especially important if you’re writing a spec for a specific show. Put it in their template. Final Draft offers a variety of existing show templates. Use the right one.
If you’re writing a comedy, get a big laugh on page one. You need to grab the reader. If you leisurely build up to the first big joke on page three you’ll find that many readers will stop at page two.
Be very sparing with interior direction. Don’t have (apprehensive), (wistful), (joyous), etc. assigned to every line of dialogue. Actors hate it and you come off amateurish.
Don’t make the character names too similar. Don’t have a Jen, a Jan, a Jessica, and a Jessie in the same script. It will confuse the reader.
If you’re writing a spec for an existing show, focus on their main characters. Don’t hinge your show on a guest star role. And especially, don’t write that big guest part for yourself.
Don’t just give one character nothing but questions. You’d be shocked at how often this happens.
Don’t have every character sound the same. You’re not Aaron Sorkin. And he shouldn’t do it as much.
Dole out the exposition in dribs and drabs, not all at one time. And if possible, in a comedy, couch a lot of the exposition in jokes.
Don’t make the script too long or too short. If MODERN FAMILY scripts are roughly 35 pages and you turn in one that’s 55 it goes right into the recycle bin.
Don’t write exaggerated accents phonetically. In other words: “I just et a biggole slice a dat pie ya’ll been bekkin.” If your script reads like a Pogo comic strip, you’re in the trash.
This is not rap music. There’s no “sampling.” Don’t copy a scene or character from another show and call it an “homage.”
Puns are death in comedy scripts. You’re going for laughs, not groans.
Service all characters in a scene. Don’t let a character go three or four pages where he’s just standing around with no lines. If a character is in a scene he needs to be there for a reason and he needs to participate.
Every scene must move the story forward. If you can lift a scene right out without it affecting the narrative of the story, it doesn’t belong there in the first place.
If you’re writing a drama, don’t assign a song to create the mood while the characters just reflect. That’s a lazy cop out. Your emotional impact needs to come from the characters and needs to be created by you, not Norah Jones.
Again, for a spec from an existing show – don’t kill off any of the main characters.
These are just a few of the things to avoid. But if you can avoid these booby traps you'll be ahead of the game in a very competitive field. As always, best of luck.