Praise Sandwich: praise, correct, praise.
I learned this idea back when I was in high school. As a student leader leading other students it was important to tell them something good they were doing, correct the problem, and give another compliment. Then as a teacher we learned this more formally. As a mom I use it all day.
You can't take good behavior for granted. As M walks across the long stretch of living room that she would love to run across, I compliment her. You certainly don't want to be scolding the children all the time. Praising them almost every time they do it right not only rewards them with your attention for going good, it reminds them to do it the right way.
Kids like attention. They will do what gives them attention. If a parent only gives them negative attention, they'll settle for that and go about getting as much as they can get.
When M or G does something that I haven't actually told them several times Not to do, I ask them "Did you know that ... is wrong behavior?" Assume they don't know because even if they did know they were probably having fun and it's hard to remember when you're having fun.
Hate the sin, love the sinner... Always refer to the behavior as being wrong or good. The child themselves is loved always. Sometimes their Behavior might make us sad, but they make us happy. This is really important because they learn that they can change behavior. If they are taught that they themselves are bad, it can lead them to always choosing actions that they feel are in accordance with that self image.
Golden Rule: Don't treat them as you would not like to be treated. I don't like to be hurried, I try to remember that when we're running behind... I don't like to be forced to eat things I don't like. I don't like being yelled at. I don't like being ignored. I don't like it when people won't forgive me and move on...