No matter what fandom you belong to whether it's Supernatural, Merlin, Doctor Who, Harry Potter, Aldnoah.Zero, Gilmore Girls, you name it, there are some rules that should not be broken.
1. Thou shalt not mix fan fiction with Canon.
I don't care how close your OTP is standing next to each other. It's not canon. I don't care how lingering their hugs are. It's still not canon. Unless it is written explicitly in the script, book, or whatever, it is not canon. Stop trying to make subtext anything more than subtext.
2. Thou shalt not over analyse.
Not everything is a symbol. Sometimes a piece of pie is just a piece of pie.
3. Thou shalt not under analyse
Just because you didn't want something to happen, doesn't mean it didn't. Sometimes a piece of pie is more than a piece of pie.
4. Thou Shalt not crap on another's ship.
Just because you hardcore ship Destiel, you do not have the right to hate on Sastiel. The expression is whatever floats your boat, not whatever sinks another's ship.
5. Thou shalt withhold spoilers.
If a new episode comes out, don't spoil the new episode! And if you do in fact leave a spoiler TAG IT AND WARN US FIRST . If I am binge-watching a series and I tell you about it, DO NOT TELL ME!
*An addendum* If it's a commonly known spoiler, it's not a spoiler anymore. If you're on a season that was filmed five years ago, nothing is a spoiler, it's fair game.
6. Thou shalt not threaten actors or creators.
THE ACTORS/CREATORS OF SAID SHOW ARE JUST DOING THEIR JOB. I do not stand for the hating and death threats I see towards these people who are just trying to tell a story that you, at some point, enjoyed, because if you didn't enjoy said show, book, or whatever you wouldn't be so invested in it to threaten the creator/writers/actors!
7. Thou shalt respect differing opinions.
Ship wars (especially if they are not canon) are stupid. You do not have to hate on people for enjoying a ship that you personally cannot stand. If someone dislikes your favorite character, you have every right to explain the importance of that character BUT you do not have the right to personally attack someone who differs from you. There is a difference in attacking and having an open discussion.
If you're at a comic con and you see a cosplayer dressed up as a character you hate, do not be disrespectful to them because there is an ACTUAL PERSON under the costume.
8. Thou shalt not crap on other fandoms.
Unless it's the Twilight fandom. Then you may have diarrhea all over them.
9. Thou shalt not be a fandom hipster.
Don't hate on something that's popular just because you want to be different. Stop saying that you hate this season, and last season, and the one before that. Obviously you enjoyed them. If you didn't like the most recent seasons, you would not be caught up and be active in the fandom.
10. THOU SHALT NOT BE A HATER!
This is pretty self-explanatory. Fandom's are about love and friendship. Fandom's should create a family, not a civil war.