Every time you sit down to write, turn it on. Make your writing time sacred except for dire emergencies. Set personal deadlines and meet them. You need to know the answers to these questions if you ever sell on a proposal. You need to know these answers to be productive.
Critique partners are great for personal deadlines.
Keep your energy level as high as possible before you write or while you write. Developing fresh and clear mental pictures which is what writers do, requires high level energy, not left-over energy. I'll skip over chocolate. Whatever it is, take the five minutes to do it before you write. I use silence or new age or classical mood music while I write.