Write every day, even if it's only a journal entry. It is a skill that gets better with practice, and the more you use it, the easier it will be to tap into that skill.
Read every day. You learn a lot from reading, whether it be what to do, or what not to do. It also helps you get the flow of the story right.
Don't give up. Writing is a long and sometimes arduous task. Even when you feel the well is dry, keep going. You can always delete it in the next draft if it's no good, but it might help get you where you want to be.