Give 'em What They Want
When you submit a script to be read, your primary goal is to remove any objection the reader has to spending a couple hours with your work (actually, your primary goal is to have them write you a check, that clears, for your hard work. But, anyway...). If the reader expects a particular formatting convention and doesn't see it, or if she sees one she doesn't expect, that'll create an objection in her mind.
By now you must be asking, "But how do I know what they expect?" The answer is simple. ASK.
Who to ask and what to ask? Also simple. If you're submitting to a specific person (agent, producer, etc.) you can call them up (a secretary or assistant will probably be just as good as the actual person) and ask if they have a style sheet or style book or a sample of a script in the format they expect. If they say no, then just follow the rules in this book and you'll be fine. If they say yes, get the sample. If you're writing a film script, it's less likely that they'll have a particular format than if you're writing a TV or Sitcom script.
In fact, sitcoms often have "bibles" that describe all the rules you need to follow to write for the show, including formatting rules. Get one. How? Call the show's production company. So, if you're writing a sample (spec) script for Veronica's Closet, call or write to Warner Brothers Television at 818/954-6000 and get their bible and/or formatting samples. Then make sure your script looks like their scripts before you send it out.
Another source for the answer to "how do I know what they expect?" is by getting your hands on a sample script which came from that production company, studio, producer, etc. Be careful though. The scripts you can buy are often not formatted properly! If you get an actual script, it might be formatted for production, not submission. If you find a script in a book, it might be formatted for the book and not in proper script format.
When in doubt, follow the instructions in here and you'll be fine.
A great source of information about what shows and films are in production, who the contacts are, and how to find them is a magazine called Written By. This magazine used to be the newsletter of the Writers Guild of America, west, but now it's available on many newsstands. If you can't find it, write to them at:
7000 W. 3rd Street
Los Angeles, CA 90048-4329
A subscription to Written By will definitely keep you informed about the latest Hollywood writer's happenings.
Now, it's obvious that you can't and don't want to reformat your script for every different reader you'll send a script to. You don't have to. If you're writing a script for an existing show, you'll only need to make sure it's in the format that show uses. If you're writing a film script or a pilot or a script for a non-existent show, and you're submitting it all over town, use the rules in this book. If you are only submitting your script to one, or just a few readers (a situation I can't imagine) make sure it's in the format that they expect. If they have conflicting formatting rules, then it's up to you to decide if you want to reformat each script, come up with a format that's a combination of their wants, or submit it in an acceptable format (like the one in this book) to all of them. Frankly, I would do the latter.
Remember, with Scriptware, if you had to reformat like crazy, it'll only take you seconds -- just tell Scriptware what you want to do and it does it, instantly!