ADVERTISE. Create a thread as early as possible in Tournament Discussion if you're expecting a large turnout. Make your post easy to read. Spell-check it. Make sure you use proper grammar. Don't make your audience struggle to get the information they need. Use colors and bold/italics sparingly, and only to highlight important information like friend codes, start times, and special rules.
CHECK YOUR TIMEZONES. gmt,bst,daylight saving ... dont forget attendees play from all around the world so its important to be clear about times , and even post several times according to the main timezones (UK and US central or Eastern time)
HOSTER(S) MUST BE ON TIME. If your tournament starts at 8PM, the hoster(s) should be there by 7:30 , adding and checking friend codes and being ready to open the room. Decide on a time to start your first event and then tell everyone to show up 15 minutes earlier. It's the only way you'll ever start on time.
LIVE CHAT IS YOUR FRIEND. IRC or any other chat system is welcome to run a tournament smoothly. last minute joining , disconnections causes , a player wanting to change controller . Remember those kind of situations are too fast to be handled by one-liner posts on the forum ,so you and the hoster(s) should be present as much as possible on the chat , to be able to deal with any kind of situations as fast as possible.
FIND HELP. Running a tournament is beyond the abilities of a single person. Ask for helpers before the event and make sure they know you'll be counting on them. Helpers can assist you in hosting rooms, screencapping result screens, announcing matches,recording videos etc...
EXPLAIN THE RULES. Make sure everyone at your tournament understands the rules, (karts only, vehicle specific , track order..).A reminder every once in a while in the chatroom or in the thread never hurts. And be sure to apply the rules equally to all players. If someone gets screwed in a race because they were told a different set of rules -- especially if they were told by you or one of your assistants -- then the race needs to be replayed.
DISCONNECTIONS . The race results should be valid ONLY when the results appear on the players screens , except for a "The race has ended.The result have been determined"-type disconnection. Restarting the race/GP or resuming the GP(or forfeiting, in 1v1s case) is entirely up to the ruleset , but its often assumed to be the latter, when the rules dont mention anything about it.
JOKE AROUND. Try not to be completely serious all the time. You're running a video game tournament, so have some fun. This will also make people like you more.
MIND YOUR MANNERS. Treat your attendees with respect.Congratulate winners when they report their victory, and encourage the losers to do better in their next races. People will respect and listen to you if you treat them well.
YOU ARE THE BOSS. Players will always complain about one aspect of the tournament or another; stick to your guns and stand by your decisions. Don't let yourself be bullied into a rule change the day of the tournament unless everyone agrees to it.
RECORD STUFF. Tournaments that put out videos of matches are just that much cooler. Ask for people who are taking part that have video cards or cameras if they can.
VERIFY RESULTS. Make sure everyone in the race report to you before moving on just in case screencapping isnt available for some reason, or have an assistant in the race watching the results.
PUBLISH YOUR RESULTS. Create a new thread about the results , 1st to last with points , or the brackets if it was an elimination tournament. In the same thread post screencaps and videos you gathered from different recorders during the races.It will be the ideal place the players to shoot out and comment about the tournament.
please feel free to add your tips as I dont have much experience in helping organizing tournaments