See as many movies as you can. Don't stick to you normal action movie or romantic comedy either. Mix it up: go to and rent movies of all different genres and vintages. Pay more attention to the story and the little details. Why the characters do what they do or say what they say? Pay attention to the supporting characters and how they impact the story on the whole.
Read more. Read books, plays, blogs... anything you can get your eyes onto. Read about all different topics that inspire you, but also ones that you do not tend to be very interested in and see what you learn. Start a classic novel you haven't read before and study the language and the way the author tells the story and compare that language to that of a more recently-written book.
Visit museums and see live plays. Visit different types of museums and watch various plays from Broadway to ones performed by your local acting troupe. See plays you have never heard of before as well as ones that are well-known. Read the books and watch the movies corresponding to the plays and compare the translations between the various methods of delivery native to each medium.
Mix up your music collection. Keep an open mind to changing what you listen to on the commute to work or during your morning run. Listen to all different types of music from pop to hip-hop and from country to classical. Listen to music from now and from when your parents were kids. Take note of how much the quality and messages in the music have changed but also what has stayed the same.
Don't overthink things. Creative thoughts should flow naturally and by opening your mind to different types of music, movies and literature you will become more inspired and reminded of things by what is around you. Take a different route to work or just cross your arms or legs differently while seated. Go for a walk outside and just stop, listen and really look at what is around you. Just take in the moment and remember all the new things you are exposing yourself to and those creative thoughts will come with more ease than ever before.