They're too little to fully understand consequences at this point. My son bites me as he cannot express excitement or frustration. I gently say no and distract or move him away. I think as a society in general our expectations of our young children are far too high
I think at this age they are literally too young to understand the concept of consequences, whether the outcome is good or bad. They can't really rationalise it. And I think listening 'properly' like we do is a skill that develops over time. So I think often distraction is the best thing to do! We used go to Hartbeeps classes and they have a song about having 'listening ears' and when I really need my daughter to pay attention I ask her to use her listening ears and she does the action from that class. But whether she follows through and really gets what I'm asking does depend! I also try to say "no" only when it's really important. Like if she's in danger. If what she's doing is just annoying I redirect her attention and hide the thing she was doing. Otherwise I think if they hear no no no all day it stops to lose all meaning.
@Kate Totally second the no thing! We use danger for serious situations and bless our lad he will completely stop in his tracks if danger is shouted (only ever used when something is legit going to kill him...he has an obsession with wires :/)
Distraction and moving them away from the thing you don't want them to do. Anything else is kind of pointless at this age.