1. Finish writing it
    Sending somebody an incomplete script makes it impossible to give complete notes; also, it makes you look lazy.
  2. Check for spelling
    The computer does it for you! Seriously, if you can't take the time to read through your own script to check for errors, you are the laziest fuck.
  3. Make sure it isn't garbage
    I know, I know; that's a matter of opinion, but really read it, and think about a person who isn't you seeing these words for the first time. Is it stupid? Is it boring? Do your characters all sound like the same person? I mean, it most likely sucks, so maybe be extra careful that it doesn't suck real bad.
  4. Listen to the thoughts of the reader
    If you give it to someone to read, you obviously care about their opinion. When they give it, pay attention. You don't have to take their notes, but at least think about them before discounting them. Otherwise, you come off like an entitled shit.