This subject comes up often enough that we should simply accumulate a list of everything that should be done, and how everything should be handled, for the novice competitor. Please add things that I have forgotten, and when everyone is done, I will compile it into a comprehensive ‘how to’ guide if others are willing.
The first thing you should have is a coach, and if you have a decent one, you need to be paying attention to them, not faceless strangers on the net. Finding a coach can be both easier and trickier than it sounds. Many superior athletes turn out to be lousy coaches, so what to truly look for in a coach is how many successful athletes they have produced. PL coaches are few and far between, and where to find them can be difficult. If you have a meet in mind, call the meet director, and they will be able to provide you with names of many of the local regulars, who might either be willing to help you personally, or put you in touch with someone who will. The remainder of this is for the athlete who does not have a coach. Go and watch a meet if you have the chance. Most occur on weekends, and it is worth the Saturday drive to see what one is like.
The next thing you need to know are the rules, which means you need to know the federation you will be competing in. A listing and summary of many federations with links to many homepages can be found here: Most federation websites have the rule book on line, and it is fairly standardized. Weight class are the same, etc. Major differences include, but are not limited to things like the press vs. the start command (IPF and affiliates use start, many old-school still use the press command), flight order (traditional flight vs. modified progressive, etc.), equipment allowed, and weigh-in times (which may also vary if you are trying to set a record - so pay close attention here). If you do not know the rules before hand, how can you expect to succeed? And go to the meeting before the competition, as the meet director may have one or two idiosyncracies particular to the meets they put on, which are normally minor, but can be enough to seriously irritate the meet director. If you think that this is in any way unfair, most meet directors are usually former competitors who no longer have the fire to compete, but are giving back to the sport in a way that is both financially and emotionally draining, as well as time consuming. In its own way, putting on a meet is more effort than competing, so if you have any complaints about a meet director not wanting people to (for example) get chalk everywhere like they are the powerlifting version of Peter North, either suck it up or go put on your own meet.
Make sure you know, and follow, the commands
The next thing you need to know is how to find the place. You might be surprised, as some meets can be held in fairly obscure locations (based on what the meet director can beg, borrow, or steal in the way of space). Some are nice, some are crowded and cramped, and some are unusual yet enjoyable (I once helped run a deadlift meet outside in front a local Irish pub, once upon a lovely summer afternoon, and the bar itself did quite well). If you are going to weigh in advance, you might be required to do this at the gym that is hosting the meet (often difficult to have calibrated scales at more than one location) so you need to know this as well. Information should be on the application (a number to call, and I have yet to meet a director who does not return calls before the meet). Get there early, and get to weigh in early. Pay early, many meets have either a cut-off point or a fee for late entries (trophies cost money, you know). In short, everything you can do in advance, do it. This way the day of the meet all you need to do is get your attempts in and lift.
Making weight. If this is your first meet, just lift, do not worry about weight, you have enough other worries.
Do not kill yourself (or at least trash your strength levels) to make a lighter weight class to break a record. If you have visions of your name on the cover of magazines, your face on the front of cereal boxes, and hordes of nubile young women chanting your name as they peel of their clothes, you can get over that right now. Your first meet is the greatest learning experience of your PL career, so focus on what you can do, not what you might be able to do.
What to wear: Most meets require a singlet and t-shirt (although the t-shirt is often not required for the deadlift), and some organizations require that the t-shirt not have a pocket. Few meets will allow you to lift in shorts (makes it harder to judge depth when squatting, as well as the fact that baggy shorts can make it difficult to tell if your bench featured a butt raise, etc.). Learn what is required in advance. Many places on line sell singlets cheaply. Get one well in advance to make sure it fits.
Powerlifting gear: Squat suits, knee wraps, bench shirts, etc. are a subject all on their own, and far beyond the scope of what I have the energy to write about at this time. If you plan on using some or all of this sort of thing, you need to ensure that it conforms to the rules (pre-meet inspection as well) as well as have someone there to help you with it. While often strangers will be willing to give you a hand, asking someone you just met to help you get into a squat suit is pushing the limits of hospitality.
Get your attempts in on time. Usually, you must give your openers at weigh in, and have one minute after your attempt on the platform to get your next attempt in. Do not automatically assume that if you miss a lift it will automatically be re-entered as your next attempt, as you have the option of increasing the lift. Generally, once you enter an attempt, you cannot change it (I write in pen for that very reason), with the exception of the final deadlift attempt, which can usually be changed twice. Also remember (I have seen people unaware of this) that if you bomb in a lift, you are out of the competition.
What to lift. Your openers should, especially at your first meet, essentially be your final warm-ups, because the number one rule is to get on the board. Allow me to make that more obvious: your opening attempts should get you on the board, so you should be able to make them with ease.
You have two more chances to increase the weight, so do not waste your first one. Lift with your head, not your ego. If you miss an attempt, find out why - ask the judges. Then repeat the same weight. While you have the option of increasing even though you missed, why play with fire? You are probably going to be even more nervous after a missed attempt, so keep it as simple as possible. And, on a personal note, if you miss an attempt, handle it like an adult. Do not yell, scream, and swear about the unfairness of life and how you are a poster child for the abused and misunderstood. I have no trouble throwing someone out of a meet for acting like this, and neither do many other judges.
Fourth attempts: As a general rule, many organizations allow a fourth attempt to set an American or World record. This usually requires a successful attempt within 20lbs. of the previous record. If you achieved this on your second, but got buried on your third, be kind to the spotters and loaders, and do not waste everyone’s time and effort with a repeat attempt that will bury you again. The spotters are the last people you should be irritating, if you really think about it.
Order of lifting: On single day meets, there is no need to worry about what day you are lifting. On two or more day meets, you need to know what day you are lifting (which will affect weigh-in, by the way, as well as what platform you will be lifting on for multiple platform meets). As far as lifting order, I am only going to discuss flight order here, as it is the most common. The squat comes first, with everyone getting their opening attempts, followed by second and third attempts. Should anyone go for a fourth attempt, this may be mixed in with the third, or follow the third at the directors/judges discretion. There may be multiple flights, so all lifters for the day will complete all squat attempts before the benching begins. The same holds true for bench attempts, followed by deadlifts. There will often be a break in between lifts (squat, bench, and deadlift) but not always, so pay attention.
What to eat: Many meets will have something, but it may not be something that agrees with you. Plan accordingly. Do not make any strange dietary changes for your first meet. If you read in some magazine that a combination of braised panda groin and candied yak rectum would provide you with an unbeatable strength combination on meet day, do not tell me about it. What you eat should provide you with energy while not filling you up excessively or bloating you. A combination of simple and complex carbs are best, without too much fat (delays gastric emptying), or be too hard to digest. Fruit is a very common source, with bananas being very popular. If you have food that you like, bring it in a cooler, along with plenty of water or simple things to drink. Avoid sugary sodas, as the last thing you need is an insulin crash before your final deadlift. And do not do anything stupid for dinner the night before, either.