New & Returning Comic Readers - Confusing DC & Marvel Rules

What is confusing about DC/Marvel superhero comics? I've been reading comics for years. I'm a former comic retailer and journalist. I'm working on an article about the secret rules of DC and Marvel Comics that new readers don't get told about. Like how does the sliding timeline work, or new number one issues, or crossover events, or variant covers? There's a lot of weird rules about DC/Marvel superhero comics that aren't really written down anywhere, and I am interested in actually making a list of them. So, when you started reading what was confusing for you? Or, if you're new to reading, what still seems confusing to you?