It really isnt a linier process, just have to let go and think.

Listen to music and think of things taht come to your mind, i used to do abstract broad paintings to try and find shapes that put ideas in my head.

Its a good idea to disconnect yourself somewhat, your ideas are influenced from what kind of things you see and read day in day out, so innitial ideas tend to be cliched, thats why music and abstract things are good. Watch films you wouldnt usually watch, art you dont usually like.