Before the Tournament
List Creation: If you're going to be playing in a tournament, you want to make sure that you have a "Take All Comers" list. Popular and powerful builds: Mechanized IG, Mechanized Spacewolves with Longfang Spam, TWC Spacewolves, Mechanized Blood Angels, Mechanized Eldar. Is your list capable of competing against these six builds? There are certainly others, but if you can stand toe-to-toe with those six builds, you'll be able to adapt and deal with other builds too.
List Printing: If have Army Builder, use it. If you can afford it, its $30 or so. Many stores have a store copy of Army Builder that you can use, and they either charge a nominal fee for its use and paper printing, or nothing at all. If you don't have Army Builder, use one of the Excel Spreadsheet Army Builders, or one of the customized and free Army Builders. Tyranids have their own special army builder....I use an excel workbook where everything is linked to each other, and has a very nice printout that shows each unit and their costs. You *MUST* bring 4-5 copies of your printed list to the tournament with you. A single copy is a no-go. A written copy is a no-go. Print your lists out and don't disrespect your opponents or the TO by offering your chickenscratch scribbled list as your list - and you should *always* be prepared to surrender your list and not get it back. You *need* a copy for each opponent and one to turn into the TO, along with one for yourself. People like me like to write battle reports, and you can't do it without a copy of your opponent list.
-Practice with your army. Practice how it moves together, what units give physical cover to others, how things move on the board and support each other; if you're playing an army with a lot of models, practice moving them quickly - like instead of moving 30 boyz 6" forward, grab the back three ranks and put them up front - you only have to move half the models. Things like that. Practice against opponents with fast armies. If you can't get through 5-6 turns in 2 hours with an 1850-2k list, practice more, or tweak your list. If you can only get through 3-4 turns in a tournament because you're slow, you're going to be labeled a slow-player at best and annoy people....at worst, you're going to be labeled a cheater who is intentionally slow-playing to avoid your own destruction and face possible disqualification. DO NOT bring an army to a tournament that you are not capable of playing in a timely fashion. These events have strict time limits and you need to be able to play within those limits.
-Tape Measure: Get the $3 12' kind from Walmart. Its small, and its great.
-Dice: Everyone has their own assortment of dice, avoid dice with custom facings. If you refuse to do so, they *must* all have custom facings on the same side (six or one) without being mixed, and you need to demonstrate before the game to your opponent which the custom sides are. Custom faces won't win you any friends, but they will be tolerated - however, if you're asked to not use them, be prepared to have other dice. Best advice: Avoid custom facings. You also will need a scatter dice if you have any kind of deep-striking or blast tempates.
-Galeforce 9 Tactical Template: This $7 treasure from Galeforce Nine is the most precious treasure to a 40k player. It's a blue template with a 1", 2", 4", and 6" side, along with a 45 degree arc of fire. When you or your opponent need to measure a close assault, or you're reaching down into a unit to move stuff around, the tactical template is far superior to a tape measure. The 2" coherency side makes disembarking from vehicles and spacing your models extremely easy. Not a requirement, but a VERY HIGHLY recommended addition to your tournament repetoire.
-Pen/Pencil: You will pretty much always need to fill out a scoresheet, so bring one with you. Keep it in your case/dicebag/foam/etc.
-Superglue: Breaks happen, and many tournaments (and pretty much all GTs) have painting and customization scores. Be prepared to fix them. For quick-setting, bring a spouted little bottle with baking powder it in - it will instantly set superglue bonds, and is also useful for reinforcing joints. I can't tell you how many times I've had Tau Battlesuits break off their stands, or reaver jetbikes, or ork deffkoptas.
-Moving Trays: Either a display board, or a couple of cookie-sheets, or a couple of fast-food trays - you need to have something to transport your army between tables. Putting your army into your foam, then making your opponent wait while the clock for your game is ticking for you to get it back out is supremely disrespectful to them - get a jump on timeliness by having something to move your assembled armies together between tables.
-Hygeine: Not joking. Fresh clothes, underclothes, freshly showered, shampooed, cleaned hair and beard if you have one, and heavily applied deoderant. Armpits, chest, anywhere else you need. Stinky gamers are a real detraction to crowded rooms, especially six hours into a tournament when your body odor is trying to push through sweat and grime to reveal itself. Keep it covered up. One of my friends brings spare deodorant to GTs and gives them to his opponents if they are particularly pungent. I realize that not everyone has the ideal personal hygiene, so you need to make a conscious effort of not being noticeable around other people for your own smell. It will mark you out unfavorably. Brush your teeth that morning, bring gum.
-Hydrate: A running monologue throughout your turn of what you're doing ,asking your opponent questions, talking all day - can be thirsty work. Hydrate, and stay hydrated. I bring two liters of powerade/gatorade with me to GTs and larger RTTs - or bring petty cash if the place you're going sells drinks. I'm a fan of drinking and gaming, and I'm personally a bit famous for the bottle of Captain Morgan that goes with me to big events, so hydration is doubly important.
-Shoes: Whatever style you want for clothes is fine, but your shoes need to have good soles; sneakers are best. Standing on your feet for 8 hours with intermittent breaks to sit is going to KILL your feet and back, so take good care of your feet and what you're going to be standing on.
-Timeliness: I can't stress this enough: If a tournament starts at 0900, you need to be there at 0830. If registration starts at 0900 and dice roll at 1000, be there between 0900 and 0930 - you need time to unpack your gear, prepare it for the games, turn in your list, register, do a bit of socializing. Do NOT be late. I've seen plenty of tournaments that close off registration 10-15 minutes before dice start rolling so that they can handle table assignments and create pairings. NOTHING PISSES PEOPLE OFF MORE than a tournament that is supposed to start at 10:00 AM that doesn't kick off until 10:30 or 11:00 because someone or a few someones were lazy and disrespectful enough not to manage their time well enough to bother showing up on time. Don't be TFG.
During Your Game
-Ask questions. Ask about things your army fears. Ask where the anti-tank is. Ask what the ranges are if you don't know. Ask about stat-lines. Ask which units are in which transports. Ask what the ICs do. Ask about special rules. As time goes by, you'll learn these things, but don't put yourself in a position of weakness by not having adequate information. Ask questions, and often.
-Don't lose sight of the objectives. Don't commit to an objective game early - killing all the enemy troop choices can win you an objective game as easily as castling up on them. But don't find yourself at the end of turn5 without the ability to jump onto objectives or accomplish the mission.
-Pick up your missed dice rolls. Do NOT pick up your hits - leave those on the table for your opponent to inspect; pick up your misses. This prevents suspicion, accidental or intentional cheating, and the possibility of your opponent saying, "Hey, you just picked up a miss!" Always pick up your misses and set them to the side so that your opponent can inspect your hits.
-Scatter dice: Roll the Scatter dice RIGHT NEXT to wherever you're scattering. There's nothing worse than someone trying to figure out the scatter direction from half a table a way, and its frustrating to have to reign someone in because they have bad depth perception. Keep those scatter rolls close. If an issue arises in the direction, there's an easy geometry fix: Extend your tape measure over the scatter dice. Have your opponent draw theirs connected to yours in a perpendicular line and hold it there. Then remove your tape measure and place it over the model / template being scattered so that the direction is true - then count out the inches.
-Measuring: There are many ways to measure your models - some people measure front to front, others middle to middle....I'd encourage you doing front to front - but the one thing you *need* to do is extend your tape measure the distance you're going to move, set it down on the table, then move your model up the length of where you're moving....then remove your tape measure. Dropping your tape measure out 12", eyeballing where its going to be, removing your tape measure and then placing your model where you saw the tape measure end is unacceptable. There's no need to guesstimate range like that - leave your tape measure on the table so that both you and your opponent can visually inspect the distance moved to make sure it is accurate. Doing otherwise is going to get you pegged as either lazy or a cheater - neither of which is an image you want to portray, even if its accidental.
-Killpoints: Don't worry about trying to keep track of killpoints or victory points during a game, except in a general sense of knowing what you need to win. You can sort those out at the end of the game.
After The Game
Post-game is an important socializing time as well. Whether you won or lost, it is important for both players to realize that it *is* a game - and that the losing side has an opportunity to learn something.
-Ask Questions: If you won, ask your opponent what they would have done differently if you played again. If you lost, ask your opponent what they think you could have done to present more of a challenge. Ask if they saw any serious tactical mistakes that you made. Losing sucks, but don't let it put you in a bad mood. Find out why you lost and don't do it again. If you won, be gracious - thank your opponent, shake their hand (either winning or losing), and ask if they want any feedback on the game, and why you think you took victory away from them.
-Socialize: A lot of gamers are shy about talking to strangers - force yourself to be outgoing and socialize with other people there. The friends you make will keep you coming back for more.
-Thank the TO: If the TO does a good job running the tournament, personally thank them. It can be a thankless job, and most of their player interaction is people asking them to rule on disputes. It means a lot for players to appreciate the effort that they've put into it.
And finally....if you have an issue during a game, bring it up during the game. Do NOT bring it up after the game with the TO, they can't do anything at that point. Don't save it for the forums as an outlet later - you're just going to cause trouble that should have been nipped in the bud. Bring up issues as they arise and deal with them on the spot; it will work out best all around.
Happy gaming everyone! I travel around the country to sample the tournament offerings of as many places as I can. If you see someone wearing a shirt with my avatar on it that says "Dashofpepper" say hi; and share a drink with me - the Captain won't be far!