My basic rule for editing: if I can't cite it, I won't write it.
It's best to use good grammar when criticising someone else's: "People that's et onions is bad judges of who's et onions and who aint." -- Thornton Wilder
I really, really do not like the use of exclamation marks in words (unless they are indicating a click as in !Kung). Using it for terms such as "!vote" hampers my reading of the comments.
We should strive to keep articles from being biased. I'm not sure what it would mean for an article to be bias; I think that has something to do with how fabric is cut. Along the same lines, a person who has a bias or prejudice is biased or prejudiced (a person is not bias or prejudice).
Demanding an apology from another editor with whom you've had a disagreement is rarely fruitful and tends just to prolong the drama. It's probably better just to let it go and get on with building the encyclopedia.
Encyclopedia writing should be formal. It is therefore inappropriate to refer to John Doe as John (but if Jon has a patrynymic rather than a surname, you should refer to him as Jon).
No matter how wonderful your best friend is, he or she is probably not a suitable subject for a Wikipedia article. Even if he or she is notable, you probably should not be the person to write it. The same goes for you, yourself. Similarly, no matter how awful your enemy, you should not write about him either.
You, are, and be are words; u, r, and b are letters. If u wish other editors 2 take u seriously and not just b annoyed at first glance, u r advised 2 remember that fact. Similarly, Do Not Capitalize The First Letter Of Every Single Word In Your Article Unless You Want To Annoy People Greatly.
Weirdness happens. Try to assume good faith. This is a reminder to myself as much as anyone else.
When making an argument, try to get your facts correct. If you want to allege that we don't use images of someone, make sure you look at the article before posting. If there are seven or eight depictions of that person, you'll look silly saying there are none.
I find it doubtful that every single person who happens to play sports at a professional level at least one time merits an article here. That seems to be the general assumption, however.
If you leave a message for me, I will try to respond in a reasonable time frame. Notice that reasonable time frame means allowing myself to go to sleep and to do other things normally associated with living a life. The same is probably true for most other editors on Wikipedia. So chill out a little before hollering that no one is replying to you, especially if they have already, but you just don't like the answer.
It seems that something like 80–90% of Wikipedia editors are male. This is no reason to make assumptions about another editor's gender.
Certain words and phrases tend to grate on my nerves. Among them are: features/featuring, due to, so-and-so revealed that, it was reported that.
"Let's please not start citing porn videos as a source in an article on a biblical topic." --Drmies
As a minimum requirement for an article's existence, WP:N is reasonable. As a maximum, I believe that itisbroken.
This user believes that userbox should always be pluralised userboxen, and thinks that this is one of the most important and exciting issues of our time.
Thi's user know's that not every word that end's with s need's an apostrophe and will remove misused apostrophe's from Wikipedia with extreme prejudice.
Subj
This user prefers that the subjunctive mood be used. Were this user you, he would use it.
Sciences
This user realizes that the Earth isn't an oblatespheroid, but rather a close approximation of one.