This general problem is why I want these signs: they call out the "shouldn't need pointing out" things in public establishments, all of which are severe impediments if you don't know them.
Of course, there is the opposite problem to worry about, of adding so many bits of advice that no one bothers reading the list, and then discounts its value, leading to people not posting these ...
Today I learned that you can toast marshmallows in the oven.
By "learned", I mean "I read a recipe which included as a step toasting marshmallows in the oven". I didn't have to try it out to realize that this would obviously work. It was plain as soon as I heard the idea. And it shouldn't have needed pointing out. I know how ovens work. I am familiar with the marshmallow species of food. I love roasted marshmallows while hating them in most other forms and often occurrently lament the difficulty of arranging open flames over which one may safely toast them. I routinely try new things in the kitchen to get results I want.
And yet I read it, and was surprised. And so were the people I reported this finding to. It needed pointing out.
What other facts need pointing out, although they are plain on inspection? What is the pattern behind these facts and a good way to find more?