Note that this list is slanted more toward nonfiction/expository writing, since, well, that's where most of my experience lies.
Six Rules of Bad Writing:
Rule 1: Use the wrong words.
Use words that don't mean what you think they do. Or words that are hideously overblown and awkward because you think they make you a Serious Writer. Remember, you paid for that thesaurus--get your money's worth!
Rule 2: Don't take the responsibility for what you say.
Don't mean what you say. Don't believe in it. Hedge. Waffle. Backpedal. Be vague (see Rule 3).
Rule 3: Stay away from the point.
Ramble on. Go nowhere. And for pity's sake, don't ever give your readers a reason to keep on reading what you have.
Rule 4: Don't have any desire to write.
Write things because you "have" to. Write them because you feel obligated to. Not because you want to. And certainly not because you need to--not because you've got something in your mind that's screaming to be let loose. No, write because it's a chore.
Rule 5: Try to please everyone.
Use cliches. Use bromides. Always avoid making yourself look bad in any way. Use commonplace common-sense conventional wisdom--and don't you even THINK about examining it.
Rule 6: Remember that any criticism of your writing is a personal attack.
Anyone who doesn't like or understand your writing is just someone who's jealous of your writing skills, or who just doesn't get your own special unique and creative vision. Ignore them. And besides, even if you did what the critics suggested, that would mean...you would have to go back and rewrite the whole darn thing! And since we've already established that the only reason you're writing is because it's a chore, why would you want to make more chores for yourself?
So, that's the list so far. Anyone is welcome to make suggestions.