A famous writer (I can’t think of his name right now) once said that he was always prepared for inspiration to strike, and that it always strikes at 9:00am in the morning.
When it comes to writing, I believe in rhythm. It’s important to write everyday, and equally important is to write at the same time, and preferably early in the morning, when our minds are fresh. This way it becomes a habit. I also like to write for at least one hour.
It’s also good to think about your story, let your mind wander, go over possibilities and dialogues and plot in your head. And then do something else, let your mind rest. Our subconscious minds are very powerful, and usually when we think about something and then give it a rest, the subconscious mind goes on working on it and coming up with amazing plot twists and the like.