Don't belittle or ridicule your kids. It can have very negative and lasting effects. Be kind, honest, and respectful, even when they're being idiots or really screw things up. Kids are like employees: if you only ever tell them what they did wrongly they will only worry about staying above that low bar. If you praise them when they do a good job they will be motivated to try and receive that praise in the future.

My four year old recently stood in my living room and started peeing himself because he didn't adequately prioritize going to the bathroom vs playing matchbox cars. He stood there semi crying and said, "Dad, I'm wetting myself, I'm sorry." I forgot my own rule and got angry at him and belittled him, I yelled, I kicked his matchbox garage over, breaking it. I will never forget the look on his face, such pain and sadness, and I was most of the cause for it. When I took him to get a bath I apologized for being so mean and we had a great talk about how I wasn't mad at him, I was mad because the carpet was dirty and I was wrong for taking it out on him. He instantly smiled and told me, "That's ok, dad, we all get angry sometimes, and I should have went potty earlier." Now, when he is playing and goes potty he tells me and I give him a high five, no accidents since.