Practice Reverse Psychology
Telling your child to do the opposite of what you want her to do works because toddlers are contrary by nature and love to assert their independence.
For example: When my 3-year-old daughter refuses to eat dinner, I'm often at the losing end of the struggle. But when I stop insisting she eat, see what happens:
"Chloe, eat your supper."
"I don't like it!"
"You love macaroni and cheese."
"No, I don't!"
"Okay, good. I'm going to go check on your brother, and I'll be right back, so don't touch that food because I'm going to gobble it all up."
I saunter back into the kitchen a few minutes later. Chloe can barely contain herself. "Daddy, all gone!" she says, showing me the empty bowl.
"What?!" I exclaim in mock horror. "I was going to eat that!"
She laughs, Daddy laughs, and dinner is over.
Of course, this strategy has a limited life span. My 5-going-on-16-year-old daughter rolls her eyes when I try this. "Go ahead, Dad. It's all yours."