For the short of time, patience or remaining-eyesight: here is a quick, ten-point tutorial for better prose.
The points are drawn from books, articles, casually-offered-advice and my own experience. Much like the Ten Commandments, they aren't all concrete rules. Just things to strongly keep in mind.
1. Vary sentence structure.
-> In particular, avoid starting every line with "I..." or "He..."
-> Try to vary your sentence length too.
2. Don't repeat words within a sentence.
-> Or too many times in sentences that follow each other.
-> Avoid repeated use of character names by using he/she where possible.
3. Avoid adverbs.
-> They clutter sentences and there's usually a better way.
-> Ask yourself, "Does this add any new information?"
4. Swap "which" for "that" where possible.
-> This is black magic. It just sounds better.
-> Also avoid "however".
5. Make pairs of adjectives different.
-> Think "big strong" as opposed to "huge gigantic".
-> Also try to avoid over-used or clichéd descriptions.
6. Check your metaphors. Double-check your similes.
-> They always need to make at least a small amount of sense.
-> If they don't, they'll jerk the reader out of the story.
7. Don't overuse exclamation marks or ellipses.
-> And really don't double them!!
-> Overuse of "exotic" punctuation can distract a reader from your writing.
8. Remove speech tags where possible. Where not possible, use "he/she said".
-> Words like "yelled", "screamed" and "cried" are distracting.
-> Make sure the reader always knows who's talking.
9. Avoid the passive voice.
-> "Bob carried Julia" is active. "Julia was carried by Bob" is passive.
-> Talk about people doing things, not having things done to them.
10. Read it out loud.
-> You can often hear problems better than you can see them.
-> At the very least, you'll catch more typos this way!