Just Obey
It’s not really that simple. Sometimes small children haven’t learned the skills or developed the self control to ” just obey.” It sounds simple but dig deeper.
“Just sit still -” Children this age are wired to move. There’s actually scientific evidence that says the moving is connected to the part of the brain learns. Have you ever had an itch that just won’t stop? That’s all you can think about, right? You need to scratch it? This is how kids feel many times. They just have a need to move.
“Pick up your toys.” What a child sees in their head when adults tell them something is many times completely different from what we envision. If you say pick up toys and they pick some they did it ! You have to use more descriptive words like put all of the animals away, but all of the blocks away,etc …
“Just be nice .” That is such a vague statement. Children don’t always even know what it means to be nice. If you ask them they may answer with things like “give a friend a toy” or “invite them to my party. ”   
One of my favorite authors posted a blog about this today and it struck a chord in my heart.

We are more inclined to teach social skills than just have our children. ” obey.”
If you think that causes mass chaos and disrespectful kids I beg you to cone visit. It’s quite different and quite lovely.