I see a ton of threads here about being banned or punished in the tribunal, so I thought i'd share some advice on combating your urge to rage when things are going poorly. I know it can be extremely difficult to stay positive when a game is slipping through your fingers, but if you follow this advice I guarantee you will never be banned.
1. Always focus on what your team is doing well. Try to type a simple "gj" or "nice" after every kill or objective your teammates produce. Praise goes a long way for morale!
2. Defend your struggling teammates if they start taking ridicule. If one teammate belittles another, you should respond with something like "calm down guys, we're still in this" or "everyone has bad matches, lets tighten up guys". Not only will this take some pressure off the struggling player, it will also help your team work together.
3. If you are playing poorly, simply apologize! Most players tend to deflect a poor play on their part to a mistake a teammate made. If you are playing mid and get ganked by an enemy playing bottom lane, instead of calling out your teammate for not calling mia, just type "please call mia's". In all reality, you died because you weren't watching the mini map. Your team will be much more effective if you just say "sorry, my bad" after a death, than raging on a teammate every time you die.
4. Never ever name call! "Noob, Baddie, Feeder" and all other expletives are almost guaranteed punishes when people read the chat in the tribunal. Get in the habbit of replacing those words with other forms of venting. During moments of frustration, sometimes its best to write nothing at all, but if you absolutely must share your feelings in chat, replace the "****" with "oops". Instead of "noob" type "no worries". Type "bad break" instead of "baddie". If it helps, you can really pound the keys while typing these.
5. Never let your team know you have given up. Don't say "surrender at 20". Don't type "we lose" or "gg" long before it actually happens. If you must initiate a surrender vote, that's fine as long as you don't flip out when it fails 3/2. This means that two of your teammates are still trying to win and you owe them nothing less than your best effort.
6. Once the match is over, type your "gg" regardless of the outcome. Once in the post game lobby, control your urge to lay blame on the not so good players. Trust me, they know they played poorly. They are probably embarrassed and dont need you to remind them they messed up. Dish out your honor to good teammates and enemy players and move on to the next match.
If you follow this advice, you will never have to worry about reports or bans, and you can take pleasure in the fact that you are a positive force in the LoL community. I'm not saying it will be easy, but trust me, once you make it a habbit, other players will start following suit. Pretty soon the game will be that much more fun and rewarding!
Another thing to consider......
This game is 100% reliant on a large community to function. More players = more money for Riot. More money for Riot = more time invested on improving and expanding the game. If you enjoy playing LoL, it is in your best interest to help make the environment as rewarding as possible for your fellow gamers. I'm sure plenty of people have downloaded this game, played a few matches and uninstalled after being flamed by people. The goal is to help struggling players become better players. This helps the community grow and also improves your odds of being matched with teammates that will help you succeed. Being nasty to people is easy, anyone can do it. There is a saying I enjoy, "Blowing Out Someone Elses Candle Wont Make Yours Shine Brighter."