1. Which direction is right or left, and/or which direction the car should go next in order to get us to the library/park/Grandma's house/home. There is no winning this fight, just pretend you're following the child's instructions or turn up the music.
2. The feasibility of visiting friends just by dropping in on them. Here's how that one goes: we can't go over there, we aren't invited. I invited us! Let's go! No, honey, they're probably eating dinner. I like dinner!!!
3. It's naptime/bedtime. NO IT ISN'T BECAUSE I STILL HAVE TO PLAY ADVENTURE HATS/READ THIS BOOK/WATCH ONE MORE TEAM UMIZOOMI/WHATEVER.
4. There will be no more popsicles today. But I get another one if I want to/if I go potty/if I put my pants on/if I give you a hug?
5. I have to go potty. Again? At this potty, too? We just went at the other store, at home, at the restaurant, and at the library. ALL OF THE POTTIES WILL BE GONE ON. It's a scientific fact that potty training preschoolers must use all of the potties, except when it would be a very good idea for them to do so, like right after a big apple juice and before a long car ride.
6. These clothes go like THIS. If the clothes will function at all in the way they were put on, do not try to fix or rearrange them. Let the child experience the rewards of putting on her own clothes while simultaneously learning that pants fit better when you put them on forwards, most of the time.
In closing, most things are not worth arguing about with a three year old, so try to talk your way around them or distract them with something shiny.