If your original creative writing looks bumbling or unpolished, it could benefit from a good edit. As hiring an editor isn't always a readily available option, most of the time you get the "opportunity" to perform that job yourself. When you wrestle with ideas, phrasing, and adjectives to place your intended picture into the reader's mind, you appreciate that writing is hard work. Editing is just as backbreaking -- a good job of editing usually takes nearly as long as the initial creative writing. Still though, it is worth the effort.
Editing is a multiple-pass project that takes considerable patience. I list below some reasonable ideas for each edit cycle. The sequence that you execute these steps may impact the style you produce; experiment a bit to see what order works best for your writing. You will know you are done editing when you are positively sick and tired of reading your work again.
Buy the best thesaurus you can find. It helps if it has a "category" section that allows you to browse by large ideas. Read your creation and look up synonyms wherever you feel a better word might more accurately describe your ideas. Be careful though: keep in mind that your audience has a certain level of sophistication and might be turned away from words that are overly complex.
Add them where you can, but try to be appropriate within the context of your descriptions. Sometimes too broad a metaphor (or too flashy a simile) can distract from the actual thoughts of your storyline. Don't mix metaphors by comparing something to a teapot only to compare it later to an automobile.
Go through your document and look up in a dictionary any words where you aren't 101 percent sure of their meaning. I've surprised myself a couple of times when I have used a word repeatedly only to look it up and find it has another meaning entirely.
You don't have to do this in front of other people. Surprisingly enough, even reclining on your sofa all alone you can immediately catch awkward phrasings and words that you are using too frequently.
Your writing will be clearer if you structure your sentences as subject-verb-object; tell action rather than describing situations. Use your word processor to search for words ending in "-ed" -- if you preceded this word by "is" or "was" (or similar verbs) the phrase would be better rewritten. Also check for the word "there" followed by "is" or "are" (or similar verbs).
Occasionally the word "not" is useful for emphasis. Most of the time though a sentence is stronger when positive; use your word processor to search for the word "not" and recast the sentence using other descriptives.
A comma followed by the word "but" is okay. Commas separating a list of things are okay. Commas setting off parenthetic expressions are okay. Other commas, however, need careful scrutiny -- should it be a semicolon, a colon, an em-dash, or parentheses?
If something sticks in your mind as being "ever so clever" you probably should remove it.
Keep related words together -- adjectives next to their nouns. The important words go at the end of the sentence; the important sentences go at the end of the paragraph.
Sometimes reading can be awkward due to the "bumpiness" of the accented syllables. Mark up your document with the accented syllables and reword singsong passages (101010) or places that have too many accented syllables in close proximity.
Finally give the document the good old spell and grammar check with Microsoft Word. This will catch any remaining flaws, however use your own discretion to violate some grammar suggestions if you are achieving special effects. Trust your ear.
You might benefit from these other sites that deal with writing:
A thorough examination of the analysis and thought required to write an essay, by a professor of political science at CUNY.
Extensive ideas for writing science fiction and fan fiction, along with excellent guidelines and examples for story development.