Send your script out to two or three people you trust to give you constructive feedback, then save it and forget about it. That's right, forget about your screenplay. When you get your feedback hide that away too. Whatever you do don't send your script out, it's not ready despite how well polished you think it might be. New writers make this mistake far too often and here's why it's a bad thing to do.
You've been working hard on your script, close to it for weeks, maybe even months. The temptation to say, 'Ah, it's done,' is overwhelming sometimes, but because you have been so closely focused on the screenplay you have become blind to any faults it has. You need time away, to have a breather and get a fresh perspective on things. Too many new writers, and believe me I've done this myself, see a competition deadline coming and start writing a few weeks before it, rushing to get the screenplay completed. By doing this they don't give the work enough time to grow and they often wonder why the don't do well in competitions. The reason is simple; your screenplay isn't ready and though you may be blind to its faults, the reader won't be. It's better to start several months before the deadline, not a few weeks. Give yourself time to get your work to a stage that is going to impress.
I'll give you a recent example of a feature I had been working solidly on for about eight weeks last year, from the first rough draft to a second more complete version. I was really pleased with it and I left it alone for three months and last week sent it to a director I know for his feedback. What he had to say was invaluable and I quote...
"I think it’s a little too idyllic for the subject matter. Everything seems to be a bit too perfect and easy for someone who’s gay and coming out in the countryside in the 60s. The only real tension comes from the two bullies. Everyone seems pretty accepting of Toby. His real obstacle seems to come from himself accepting, but there doesn’t seem to be too much soul searching."And because I've had that space from the screenplay I can also see that now, I even saw it when I reread it, before I even looked at the director's notes. His feedback just confirmed what I was already thinking. So of course the next rewrite will concentrate on the point he raised.
So once you've had a gap away from your screenplay say after a month, maybe two, open your document again and reread it, making notes as you go. Write down where you think the screenplay is weak and what you can do to improve it. Then, and only then, read your feedback notes, at least twice. Compare those notes to yours and make further notes if you need to. Then put it all away again for a couple of days.
When you come back to your screenplay read it again and the notes. By now the notes would have sunk in and you should have a very good idea of where the screenplay falls short. The rewrite will now be a lot easier. When it's done you'll have a well rounded script. Of course the more times you can repeat this the better your script is going to get. I would suggest doing this at least three times. When you see the amount of constructive criticism reducing then you know your screenplay is ready.
Have fun and happy writing.