1. Read and write a freaking lot. By reading works of different authors, one learns to distinguish different styles and develop his/her own. By making a habit out of writing even one page everyday, one learns to work continously. And always, but always stop working when you know what you're going to write next. I have, myself, stopped working on some certain projects because of the Writer Block that I couldn't pass.
2.Rewrite. Always rewrite. Write a scene from different points of view, use synonims of the words that don't feel right, try to make it perfect. Ernest Hemingway wrote the final scene of "Farewell to arms" 39 times before he was satisfied. I don't mean to say you have to do that too, actually I have heard of people who tried rewriting but figured out their first draft was almost always better than the second. The point is, there's almost always room for improvement.
3.Be a sadist. That's what many say. Don't shelter your character, no matter how much you have attached to him/her. Make him/her go throught the hardest times, the most miserable situations, in order to let the readers see what he/she is made of.
4.If you don't have fun, you might as well put the pen¬ebook down, turn the computer off and start going to piano lessons.
I hope these few ideas will help you as much as writing them all down helped me. And here are a few helpful links that made it all much clearer to me.
http://oldsite.greatwriting.co.uk/content/view/312/74 - a Stephen King interview.
http://www.victoriamixon.com/ - the website of a great editor.
http://www.futureisfiction.com/ - random plot points that are good inspiration boosts and many other stuff.