Set your routine. Routine will help you. Establish a particular time of day, location, and atmosphere for your writing sessions.
As you establish this routine, the creative side of your brain will become accustomed to working in these familiar conditions. Things to consider are…
Noise: some writers enjoy absolute quiet. It's similar to a musician practicing music in silence. Others will listen to music to jog their creative juices. Others will want the company of friends to bounce ideas.