First read everything you can about writing and making it as a writer, including Writer with a Day Job: Inspiration & Exercises to Help You Craft a Writing Life Alongside Your Career, by Áine Greaney.
A few of her pointers:
1. Plan your first drafts in your journal in order to free yourself from your editing self. Make a list of the themes that you see recurring in your journal. Those are what you should be writing about.
2. Listen to music rather than news to and from work, or drive in silence to allow your creativity a chance.
3. When you see an unusual license plate or bumper sticker in front of your car (while keeping your eyes on the traffic), think about what sort of person might have chosen it. Where is she from, who is her boyfriend?