Here's a quick way to make your script more professional: search every scene for the word 'laugh.' Then - and this is the hard part - be honest with yourself about if the laugh would happen in real life.
I just got through a script where whenever the words 'she/he laughs' appeared I mentally added '...for no discernible reason.' It made the story sound like a bad 80s sitcom with canned laughter added far too many times.
If the situation isn't supposed to be funny call it a nervous laugh, or a laugh to break the tension. That's fine. But if it is supposed to be funny and isn't either make it funny or don't indicate that everyone finds it hilarious.
Remenber, a smile will let us know someone is being found charming or cute, and is a better choice if the situation is only debatably funny.
