1.) Furry characters shall not have a human facial structure (jaw, chin, eye socket, etc).  They shall have the base animal's facial structure, though it may be stylized.  Human hair on the head is OK.  
2.) Furries shall not have human lips.
3.) Furries shall have animal paws with pads, not human feet with long toenails.
4.) A comic that involves noble furries fighting for freedom against evil hyoomans shall be an object of scorn.
5.) Art theft is a great excuse to feel important.  Steal each other's art regularly and everyone wins.  If Disney steals your art, that's even better.  Write them angrily and frequently if you even suspect your character's likeness was used.    
6.) Screenshots of your furry character from online games, 3D chats, video games etc. are not worth seeing.  Neither are scenes made from 3D models, unless you designed the model yourself.  
7.) "Sexy" characters shall not be based on domestic animals ("cute" characters of these types are ok).
8.) Female characters shall not have excessive visible fur texture on their chins and chest.
9.) No matter how many breasts the female of the base animal form has, only 2 breasts are acceptable.  
10.) A cartoony style is almost always preferable to a realistically rendered hairy person with a wolf head and tail (usually seen with an incongruous assortment of Native American imagery).  
11.) Furries shall be portrayed in evolutionarily realistic colors.  If "evil teen" colors like neon green and nuclear orange are used, reduce the cliche by limiting the number of piercings to about 10 percent of your ideal number.  
12.) Drawing nonhuman characters does not allow the invention of muscles not analogous to the human physique (aka "it's just MAI STYLE").
13.) The anthroform of the base animal shall have that animal's tail.  
14.) Even though it is impossible, tattoos are OK.
15.) There is no predjudice against furries... only against the socially-inept, and a widespread general dislike of bad art on the internet.
16.) You do not have the soul of an ancient dragon from the Ming Dynasty.
17.) Do not draw furry because it is "easier to draw than humans."
18.) Use words like "yiff" and other fandom jargon only ironically, and at your own peril.
19.) Human to animal photomanipulations are deeply disturbing.  "Real" furries (genetic modifications, alien characters and such) would probably look like this.  
20.) Humans romantically involved with furry characters is a big no.
21.) "Taur" characters are wrong on so many levels.
22.) Reptilian characters are best portrayed as slavers in classic sci fi and space opera.  
23.) It is best to draw influences from more than just The Lion King for expressions.
24.) Don't name your characters anything with an apostrophe in it (see also names such as "Moonclaw Firewing, Ebon Darkfur, et al.).
25.) Furry For No Reason fan art of non-furry characters should be limited, if it is done at all.  
26.) FFNR Jack Bauer is a leopard, always.
27.) The Egyptian gods were not furry, but it is OK to make them so.
28.) If a furry story does not deal with the socio-political ramifications of a character's furriness and its place in their society, or a unique alien culture, it is a regular (probably bad) story with ears and a tail (FFNR).
29.) Limit color adjectives drastically in your character descriptions.
30.) If people mention CSI when they see your art, pretend you don't know what they're talking about.
31.) Don't blame your scanner.  It's not its fault.
32.) Stop justifying your furry nazi characters with "the uniform looks cool."  
33.) Sonic is not furry... he looks like a turnip with anime eyes, and a black olive stuck on a hotdog for the mouth
34.) A sensibly dressed smiling cougar tending her herb garden colored with markers may sell prints at conventions, but it's still boring.
35.) Improve improve improve.  Study art from all areas.