I think you should be sure to follow all the rules you learned in school pertaining to Introduction, body, Conclusion, transition sentences, thesis sentence, etc. Also spellcheck it for dangling participles, split infinitives, and passive voice. Make it active! Beyond that, I'd say make it come to life! Let it draw in the reader, let me visualize whatever you are talking about, and if it is an emotional story, let me feel like I am living it, rather than evoking pity or sympathy. I know that is a tall order to fill. . . so, start by simply capturing the raw feeling of what it is you want to say, and then go back and clean it up so it says it in the right way. When you write in this manner, you will find that your writing is powerful, because, you have captured your true feelings. When you try to write it correctly as you go, it slows you down, and you lose momentum. Trust me on this one!