There's this stereotype that, second only to Swedes, Canadians are the most used to standing in line (except for people who live in countries with chronic shortages, of course).
I don't think this is strictly true -- I've stood in plenty of lines in the USA as well -- but there's no doubt we have a form of "line etiquette" that many hold sacred.
These tips are for those who don't seem to understand lines.
First, observe what others are doing. Maybe the venue has a standardized lineup ritual, or maybe something has formed spontaneously, but in either case you can get a sense of the situation by watching others.
Is there a sign that says "line starts here?" That's a good indication that the line starts where indicated. Are a line of people standing at the sign? If so, go to the end of the line and -- when in doubt -- ask if that particular line is the one you're looking for.
If nobody is lined up behind the sign then you can feel free to start the line yourself. Patiently.
Never step in front of others. In some situations it may be okay to join friends in the line, but usually only if the line is incredibly long or if the line is moving quickly. If the line is short then you should go to the end, otherwise everybody will call you "butter, butter, peanut butter," if only in their heads.
Never take the express line unless you meet the line's conditions. I don't care how old and tired you are.
If everybody is frustrated with the line's slowness, it's okay to make disgruntled comments. But know when to quit. It's bad enough waiting forever in a line without having to listen to somebody huffing about it.
When you are at the front of a line which leads to personal service with more than one wicket, wait until you are called. Never just pick a wicket and walk to it. The person at the wicket may not be ready for you, or there may be a system involved.
If you walk directly to a wicket without being called then you are setting yourself up for a disappointment; what if the wicket closes on you? What if the person isn't ready for you, and meanwhile the people who were in line behind you are filtering over to other wickets which have suddenly become available?
Greed and haste is usually punished in this situation.
When you are at the front of a line and waiting to be called, pay attention. Do not get lost in a conversation with your friends. Do no use your cel phone. Beside the probability that you will not notice when you are being called, it is also very inconsiderate for a service person to have to compete for your attention. Remember, you don't like it when THEY chat behind the counter, do you?
When you are being served, remember how it felt while you were waiting back in line. That's how the people behind you feel now. Do not chit-chat with the service person. Do not make a scene. Do not make outrageous demands. You wouldn't want to wait while somebody else does that stuff. Get your stuff and move along.
If the server made a mistake, you are allowed to come back and go directly to the server without waiting in line, but only if you are in a hurry or if the problem can be quickly resolved. When servers make mistakes, rules can be bent. If, however, you just want to take out your anger about having stood forever in line and then gotten the wrong stuff, save it for a time when you won't make other people suffer. Believe me, people don't respect you when you hold up the line. They think you're stupid.