I have looked through some of our old rule threads for ideas, but I'm going to ask anyway

We want to institute some specific rules, but we want them to be understandable and appropriate for our 4 year olds. We already have no hitting, ask to be excused from the table, no throwing hard things, and the like from when they were younger.

Now we want to institute a rule about tv/screen time
I'd also like one about not saying "I hate that" at dinner before you try it

But what kind of rules do you have or did you have at this age?