Two years after graduating from film school, I have found it to be a struggle in finding criticism. Criticism makes writers much more effective.
Take advantage of the criticism you receive in class - instructors and classmates. Once you leave college, people will not want to listen to your work. Essentially, you will have a tough time finding feedback.
Constructive criticism that helped you in college will later turn into repetitive criticizing and judging. People may in fact criticize your work for reason of holding you back from attaining your goals.
Make sure you get as much criticism as you can. There is going to be a time when people will avoid taking the time to assist you with the writing process.
Remember to ask questions about your screenplays and creative writing pieces. Constructive criticism outside of the academic sector is not as useful unless you find a writing position that provides it.
Writing contests are good forums for feedback, but impersonal feedback is much more reliable.
Good luck on your writing journey.