These are the ARAM commandments as I see them. In the absence of an actual queue with matchmaking, can we all just agree to follow the commandments?
One - Remember: It's Random
Don't dodge because you didn't get you favorite champ, or your team composition is undesirable. Man up and deal with the nature of the randomness. If you ARE going to dodge, at least have the consideration to do it within the first 10 seconds. Waiting until 3 seconds are left and then dodging is so much more infuriating than an insta-dodge
Two - Don't Quit on you team
Remember, it's random. Not everyone is going to get their best champ, particularly with free week champions who they may not even own. Don't leave the game, intentionally feed or go afk just because you have a 'noob *insert champion name here*' on your team. You'd be surprised how much better people get with a new champion by the end of an ARAM game with constant team fights.
Three - Don't be Afraid to Communicate
It's OK to communicate with your team, especially if you know you have a champion that is a good initiator. If you have Malphite, let your team know how long your ult is on CD for. If you have Sion, tell you team to make sure they annihilate Yi when you stun him after his next Alpha Strike. Even if you don't have a good team composition, you can win if you communicate better than the other team
Four - Keep an Open Mind
The Proving Grounds are very different than Summoner's Rift and not everything that works on SR will work on PG (and vice-versa!). If you know something works well on a certain champion in PG, let your teammate know. If he went AD Yi, he probably doesn't know just how hard AP Yi can destroy the other team. Don't blame him, blame yourself for not telling him when he bought that first Vamp Scepter or Doran's Blade.
Five - Master Yi is Evil
Just come to terms with the fact that Master Yi is an evil, sadistic ******* in the Proving Grounds. The sooner you accept that, the sooner you can shut him down. If you shut him down early, you can at least keep pace with his damage and take him out of team fights early enough so that he's not scoring pentakills left and right.
Six - Defense Wins Games
So many times, I've seen teams build ALL damage and then just get destroyed by the other team who has a champ or 2 that can absorb most of the punishment and let their team mop up when everything is on cooldown. A little defense goes a long way. Even if your champ isn't designed to be a tank or support, it's ARAM, think outside the box! Work with what you were given.
Seven - Don't face check at Level 1
First Blood! If you have an urge to face check those mid bushes at Level 1... Don't do it! Especially if your whole team isn't there yet. This is especially true against teams with certain champs (Blitz, Lux, Morgana, Sion, Taric, Pantheon... many more) that can potentially chain CC you, because you WILL die before you can even waste your Flash. Curiosity killed the *insert face checker here*. Let your teammates scout those bushes with their skills if they have them. If no one can, just hug the tower for the first couple of minutes.
Eight - All Champions have a power curve
So many teams get down early and just give up. What they don't realize is that many of those champions that were destroying you for the first 5 minutes won't get much stronger with items. If you have a team with a few ADCs and Bruisers, you will probably be tower hugging early against a team with a lot of poke. But most of the time, once you get a few items, you can just dive in and melt that poking team in every team fight. Gather your team (wait for respawns) and force a full 5v5 fight and you might find that you're actually stronger than the team you were scared of a few minutes prior.
Nine - Don't be a jerk
Super simple stuff. Jerks just make things less fun for all involved, which leads me to...
Ten - Play to have fun!
Everybody likes to win, but you can't win (especially in LoL) all the time. It just won't happen. Just try your best, work with your team and enjoy yourself. I realized a long time ago that this game is so much more enjoyable when you stop worrying so much about winning and losing, particularly in a game mode where you have no control over who you're going to be playing.
Anyone have more?