I've used this a lot for all of my formal writing and adhere to most grammar rules and such for forum and game writing.
I think everyone here can benefit from this, especially the new high school students who need to take the new SATs that requires a written essay.
If you do not know something on here, whether a word or where the mistake is, just ask, you'll only look really stupid.
I would recommend you copy and save this as it really helps in college, and probably all your future endeavors.
The ones I like above the others bold in blue. 
Fifty Rules for Writing Good
1. Each pronoun should agree with their antecedent.
2. Between you and I, pronoun case is important.
3. A writer must be sure to avoid using sexist pronouns in his writing.
4. Verbs has to agree with their subjects.
5. Don't be a person whom people realize confuses who and whom.
6. Never use no double negatives.
7. Never use a preposition to end a sentence with. This is something up with which your readers will no put.
8. When writing, participles must not be dangled.
9. Be careful to never, under any circumstances, split infinitives.
10. Hopefully, you won't float your adverbs.
11. A writer must not shift your point of view.
12. Lay down and die before using a transitive verb without an object.
13. Join clauses good, like a conjunction should.
14. The passive voice should be avoided.
15. About sentence fragments.
16. Don't verb nouns.
17. In letters themes reports and ad copy use commas to separate items in a series.
18. Don't use commas, that aren't necessary.
19. "Don't overuse 'quotation marks.'"
20. Parenthetical remarks (however relevant) are (if truth be told) superfluous.
21. Contractions won't, don't, and can't help your writing voice.
22. Don't write run-on sentences they are hard to read.
23. Don't forget to use end punctuation
24. Its important to use apostrophe's in the right places.
25. Don't abbrev.
26. Don't overuse exclamation marks!!!
27. Resist Unnecessary Capitalization.
28. Avoid mispellings.
29. Check to see if you any words out.
30. One-word sentences? Never.
31. Avoid annoying, affected, and awkward alliteration, always.
32. Never, ever use repetitive redundancies.
33. The bottom line is to bad trendy locutions that sound flaky.
34. By observing the distinctions between adjectives and adverbs, you will treat your readers real good.
35. Parallel structure will help you in writing more effective sentences and to express yourself more gracefully.
36. In my own personal opinion at this point of time, I think that authors, when they are writing, should not get into the habit of making use of too many unnecessary words that they don't really need.
37. Foreign words and phrases are the reader's bete noire and are not apropos.
38. Who needs rhetorical questions?
39. Always go in search for the correct idiom.
40. Do not cast statements in the negative form.
41. And don't start sentences with conjunctions.
42. Avoid mixed metaphors. They will kindle a flood of confusion in your readers.
43. Eliminate quotations. As Ralph Waldo Emerson said, "I hate quotations. Tell me what you know."
44. Analogies in writing are like feathers on snakes.
45. Go around the barn at high noon to avoid colloquialisms.
46. Be more or less specific.
47. If I've told you once, I've told you a thousand times, exaggeration is a billion times worse that understatement, which is always best.
48. Never use a big word when you can utilize a diminutive word.
49. Profanity sucks.
50. Last but not least, even if you have to bend over backward, avoid clichés like the plague.
Read; Learn; Love; Apply.
~Shadow
