ADVERTISE. Create a thread in your regional zone forum, or in Tournament Discussion if you're expecting a large (50+) 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 addresses, start times, and special rules. Large tournaments can benefit from posting threads in regional zones asking for help with equipment and housing.
BE ON TIME. No one else will. If you open the venue at 8AM, be there by 7:30. Decide on a time to start your first event and then tell everyone to show up an hour earlier. It's the only way you'll ever start on time.
COMPUTERS ARE YOUR FRIENDS. Bring a laptop to the tournament and find a piece of software to help run it.
Tournament Maker 2 is a popular choice, but there are
superior alternatives. Download the software ahead of time and make sure you know how to use it. Bring speakers and a microphone if you have a soft voice. Also consider bringing a second monitor -- most laptops (and PCs with dual-head video cards) will let you mirror your display onto the monitor, so your players can view the bracket without crowding around the computer.
DON'T TAKE MONEY FROM THE POT. The only time it's OK to take money from entry fees is to pay for venue costs. The electricity cost of running one TV for 10 hours is negligible, so don't use your utility bill as an excuse to charge money. You aren't running a tournament to make money -- unless you actually are, in which case there are FAR better things you could be doing to that end -- you're running a tournament because it's FUN.
EXPLAIN THE RULES. Make sure everyone at your tournament understands the rules, from counterpicking to random stages to double blinds; having printed rule sheets available at each station is also effective. This is especially important for non-standard brackets like round robin pools. And be sure to apply the rules equally to all players. If someone gets screwed in a set because they were told a different set of rules -- especially if they were told by a staff member -- then the set needs to be replayed.
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 collecting entry fees, monitoring stations, preventing friendlies from taking over, running pools, announcing matches, setting up, tearing down, and reporting scores.
GIVE PLAYERS A CHANCE TO REVIEW THE BRACKET. Ask them to alert you if they play one of their friends or crewmates early in the tournament. While you're under no obligation to change such a scenario, it really isn't much work and will make them much happier. No one likes to play their friends in a tournament. Some software programs will automatically create a bracket so players from the same location don't play each other; figure out if yours does and use it if you can.
HOST SMALLER TOURNAMENTS BEFORE GOING FOR THE BIG TIME. Don't try to run a regional bonanza without throwing a smaller local tourney first. You'll learn more than this thread could ever teach you and people will learn to respect your name as a tournament host. Respected hosts get the big turnouts and the hot chicks (it's true).
INTRODUCE YOURSELF. Make sure everyone knows your name and what you look like; the best time to do this is when taking signups. Ask the name of everyone you don't know and tell them yours in return. It's as good a first impression as any, and someone who likes you off the bat will be much more forgiving when you yell at them to stop playing friendlies later on.
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.
KEEP YOUR EYE ON THE PRIZE MONEY. Do not leave it in a public place. Your pocket works fine, but a locked cashbox hidden somewhere is better. Keep prize pots separate (don't mix teams and singles entry fees). Don't give the money to anyone you wouldn't trust with your first child's life.
LABEL YOUR STATIONS. Give them numbers and reference those numbers when announcing matches. NEVER TELL SOMEONE TO "just find somewhere to play." Try and keep track of who's playing where, and which stations will be open soon -- the right computer program can help with this.
MIND YOUR MANNERS. Treat your attendees with respect. Treat the owner of the venue with even greater respect, and do everything in your power to protect it from damage. Don't use a microphone unnecessarily while a big match is going on -- hearing weird sounds coming from a PA system can be very distracting. Congratulate winners when they report their victory, and encourage the losers to do better in their next matches. People will respect and listen to you if you treat them well.
NEVER LEAVE THE DESK UNATTENDED. Make sure someone is always at the front desk guarding the brackets. It's very easy for someone to quickly change your bracket or modify the pot size if you aren't looking. Have an assistant standing by for when you have to play your matches.
OPEN EARLY. Everyone wants to play friendlies during a tournament, but doing so slows everything down. So open early and let people get their friendly matches in ahead of time.
PUBLISH YOUR RESULTS. And not a sparse listing on who got first/second/third. Put copies of your brackets online; most tournament software will let you copy a bracket image, which you can paste into Paint and then upload to a website like imageshack.us or imagedump.com. A bracket image will let players see who they beat and lost to, which is much more interesting than what placing they achieved.
QUEUE MATCHES. Put matches in the on-deck circle for each station. As soon as the current match finishes, the players behind them take over while the original pair reports their score. This helps keep the tournament moving with maximum efficiency.
RECORD STUFF. Tournaments that put out videos of matches are just that much cooler. Ask for people to bring VCRs (they're surprisingly hard to find) and gather some tapes. Try to put your best matches on TVs with VCRs. But let someone else worry about starting the VCRs at the right time (you do have a staff, right?).
SEED YOUR BRACKETS. Skilled players hate entering tournaments where brackets are randomly assigned, because doing so makes results much less valid than a seeded bracket. Try to seed at least the top eighth of your entrants -- for a 64 man bracket, this means seeding the top 8 players in order. Group the rest of the players based on relative skill levels (beginners, intermediates, experts). Then create the bracket. Some software programs don't allow you to mix grouped seeding with manual seeding; in this case you should go with groups and manually fix the bracket to the top X players appear in the right slots.
TEACH YOURSELF BRACKET THEORY. Make sure you understand the logic behind double-elimination brackets.
Wikipedia is a good place to learn the basics. Pay attention to how first-round matchups are scheduled, how and where players drop into the losers' bracket, and how changing a player's seed moves them around the bracket. In case of a computer malfunction, you may need to continue a bracket by hand; make sure you understand bracket theory well enough to do this.
USE COMMON SENSE. Self explanatory. Should you show that random guy where you're hiding the money? Can you trust the word of Joe Smasher if he tells you he just beat Isai? Is it a good idea to leave the venue while the tournament is still running? Should you make sure to remind players to remove their memory cards after setting up their Cubes? You should rethink your desire to host tournaments if the answers to those questions are ambiguous.
VERIFY RESULTS. Make sure both the winner and loser of a match report to you before moving on, or have a staff member watch the result. Even MLG tournaments have been tainted by improper reporting of results.
WHO YOU BEAT IS EVERYTHING. Try to emphasize to your players that their overall placing is not as important as who they beat or lost to. Someone going against Ken and PC Chris in two consecutive matches would get last place in said tournament. That isn't fair, and isn't as important as the fact that they only lost to the top two players in the nation. Try and convince your players to pay more attention to the Who (they beat) than the What (they placed).
X IS A DIFFICULT LETTER TO USE.
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.
ZOMG I ONLY CAME UP WITH 24 TIPS. Oh well, I tried :).