1) Make sure the plot of your story is well worked out, and how the unfolding tale impacts your characters. It makes the writing process for you all the easier.
2) Make sure you have your characters worked out and how they interact with each other, where the tensions and conflicts lie within their group. That creates drama and reality. Remember; the story is not so much about what happens as how events affects your characters. That's what gives it emotional depth and resonance - that's what makes the reader connect with the tale.
3) Write every day. This was the late, great Ray Bradbury's advice to writers, and I try my best to live it. Make writing a discipline. Even if you can only squeeze out fifty, a hundred, two hundred words a day, you can look back at the end of each day and tell yourself honestly that you spent time writing and got something down. It's amazing - even if you only manage a a little a day - how quickly it all adds up, and it's a confidence booster too.