When describing a scene, person, or "thing" in your writing, be specific. Telling the reader "the desk was made of wood" or "he didn't feel well (not good)" is weak writing. If the desk was made of wood, then tell us what kind of wood. A light-stained oak? Mahogany? Knotty pine? If your characters is ill, then tell us what ails him.
Go through your text and remove any weak nouns, verbs, and modifiers. Eliminate abstractions and replace them with concrete images. Help your readers visualize what is happening.
Cut any clichés, unless they are central to your character. If you use a metaphor or simile, create your own.