• Avoid run-on sentences they are hard to read.
• Don't use no double negatives.
• Use the semicolon properly, always use it where it is appropriate; and never where it isn't.
• Reserve the apostrophe for it's proper use and omit it when its not needed.
• Do not put statements in the negative form.
• Verbs has to agree with their subjects.
• No sentence fragments.
• Proofread carefully to see if you any words out.
• Avoid commas, that are not necessary.
• If you reread your work, you will find on rereading that a great deal of repetition can be avoided by rereading and editing.
• A writer must not shift your point of view.

--Courtesy of Wikipedia, originally from The New York Times, 1979