Whatever you do, don’t use G2A and other similar CD key reseller websites. Developers would rather you just pirate the game because a lot of those keys are stolen, which cause a charge back that ends up costing the developers tens of thousands of dollars in fees. In rare cases it has even bankrupt them.
I’ve got one more to add to your list, and I hate it, but it’s worth mentioning: https://en.m.wikipedia.org/wiki/Hungarian_notation
It’s when the data type is in the name of the variable.