Write a lot. Read a lot. Brandon Sanderson had to write five novels before he sold one. Read every day. Read Strunk and White. Learn the rules. (Yes, writing has them.) Get a giant wall calendar showing every day of the year. Set a writing goal and every day you meet it, draw a line. After a few days you have a line segment. Don't break the line! Convince yourself that reading and writing is "work" and don't let friends and family tell you otherwise. Find a room with a door. When you're writing, close it. Don't edit when you write. Move forward, forward, forward. Get to the end. If you need help with motivation, read these books.