One of my favorite parenting tools was taught to me by our "Parents as Teachers" lady who came to our home when our son was young to assess his readiness for school.
She asked if we were having any parenting challenges with our four year-old son, John. I said it was often hard to get him to take a bath at night. She said, "Have you tried giving him a choice?" I remember my reply was "Bath is not a choice!". She explained not a choice about whether to take a bath, but how he'd like to get to the tub. I have to admit I thought she was crazy, but that night about 8 PM, I said "Do you want Daddy to carry you to the bathtub John or would you rather skip back there on your own?" He proudly exclaimed "John will skip back himself!". To my amazement, by the time I caught up with him he was taking off his clothes in his bathroom. It still amazes me how well this tool works with kids.
A big part of childhood development is something called autonomy. As they grow they want to feel like they have some choices in their life. Some control of their own destiny. Who doesn't want that? If it is their idea, they are way more likely to do something. The next time you run into a resistant child, offer them two options that are both acceptable to you and see how it goes.