"Join a screenwriting group."
No other source will help you more than peer reviews and discussions related to everything screenwriting, film, and news. Also, being in the company of other writers and entertainment professionals has a motivating and inspirational effect. So get out there and join a local screenwriting group (check out Meetup.com) or find a reputable community such as the #scriptchat discussions via TweetChat.
Scriptchat is a weekly online check-in that leverages the Twitter platform (Sunday @ 5pm PST / 8pm EST). It's a great way to get involved in that week's agenda, have an opportunity to speak with industry professionals, and network with other writers.
Another idea to is test your writing by using online resources such as Feedback Friday (submit your first 10 pages, the critical portion of your script that will determine if a reader/producer will continue to read your script or trash it).
Or feel free to submit your script to this site - Screenwriters Anonymous - for a free review and rewrite service (yes, FREE). Have Act 1 completed? Then send it along? Have an outline you want to bounce off somewhere to ensure your storyline has a good flow with the all-important plot points. We'll give it a whirl. We're most interested in comedies, thrillers, and crime features or short scripts, but will leave the door open to all genres. The feedback will generally be a one-sheet touching on the essential elements of screenwriting (i.e., concept, story, characters, dialogue, structure, writing style, and general notes), but if we require additional pages, then we'll gladly provide this to you.
Have questions about formatting or other related screenwriting concerns, then please send your email to Screenwriters Anonymous.
The only thing we ask in return is that you give us permission to post your review on our site for others to see as a sample. We will remove your name and title to protect you and your work.
Have another online or "brick & mortar) community you'd like to add to this? Then drop a comment in the space below.