First Come, First Served
A line forms at the front door (usually) and everyone keeps their own place in line. Yes some people will walk around and talk once they have established a place in line and this is generally accepted. But, leaving the property usually means you have abandoned your place in line and will have to go to the end of the line if you return. Many an argument has started over this situation. When you get in line remember you are responsible for knowing who you are behind and even how many are in front of you.