Ignore the Punctuation

How to make your script sound conversational
As writer, I think deep down I want to please my 7th grade English teacher, Mr. Poncia, by making sure all of my punctuation is grammatically correct. The problem is, we don’t speak with grammatically correct English. We speak in partial sentences, repeat words, stutter and stumble, use the wrong words, etc.
So, how do you make grammatically correct English sound conversational? You ignore it. Tell your actors, “Don’t stop and pause when you come to a period. Just roll right through it.” And, “stick a comma in where one’s not written.” The point is, if you want to sound natural, chances are you can’t read the words exactly as their written.
Same is true for “ad libs.” I always give my actors the freedom to “bring something to the table” because they may very well have an idea that I haven’t thought of and it makes the spot better. And that’s especially true when their reading the script.
And this is another reason to write “short.” Inevitably, an actor will give you a great read, but now your spot is :62 and you have to cut. Much better to write a :57 spot so that you have a little time to add something unexpectedly great.