I was inspired by @engin_arlak’s post here The ultimate developer jokes thread! (worked better for my wife 
):
Here are some psychological tricks that can be used for kids, but also with managers or customers 
Ask for more
Starting with a big, tough request (like asking the kid to clean the whole house), so that when you follow it up with your real, smaller request (clean their room), it seems way easier and they’re more likely to say “yes.” It’s a sneaky way to make your actual ask seem like a no-brainer! Just remember, keep it fun and friendly!
The power of choice
A better option than just asking someone to do something is to let them choose between two options. They will feel more empowered and less likely to resist. “Either finish your meal or go to sleep”. Of course they might choose the option you don’t like that much
Don’t give much time
Giving too much time lets the person think it over or even come up with an excuse why not to do it. A smart trick is to make something seem like it’s running out or only available for a short time, which can push people to make a decision quickly. Say “Hey, I bet you can finish your homework before the timer runs out in 30 minutes! If you do, we’ll have extra time to play a game together.” By setting a time limit, you’re creating a scarcity of time, making them more motivated to complete the task quickly to “win” the game or reward.
Do you use any of these or know other tricks?