And don't start sentences with a conjunction.
If you reread your work, you will find on rereading that a great deal of repetition can be avoided by rereading and editing.
Never use a long word when a diminutive one will do.
Unqualified superlatives are the worst of all.
If any word is improper at the end of a sentence, a linking verb is.
Avoid trendy locutions that sound flaky.
Last, but not least, avoid cliches like the plague.
~William Safire, "Great Rules of Writing".
Another important rule about writing - Show, and don't tell. Do you prefer to write by telling what is happening? Or do you prefer showing what is happening in your story, rather than telling?
If you want to know more about how to do it, please read this informative post, written by an experienced editor.