You can never say enough nice things to a child. Children love to be praised and respond to it much better than to criticism. Unfortunately, most parents tend to give kids attention when they are misbehaving rather than when they are on track. Even if this is in the form of eye contact, yelling or punishment, attention is attention and it means the world to a child. In this busy world, we can get more focused on what they AREN'T doing rather than what they ARE doing right.
The truth of the matter is, you are more likely to reinforce behavior with positive feedback than with punishment. If you want to change your child's behavior, give them attention when they show you signs that they are doing the behavior you want (even if its just effort and not the exact behavior). Additionally, people are more likely to respond to the positive than the negative. Research shows that people are more likely to follow directions if you tell them what TO DO rather than what NOT TO DO. For example, rather than saying "stop running" we could say "please walk". Or rather than say "keep off the grass", we could say, "walk on the side walk". For a child, you can say "You are playing so quietly with your toys" or "You are such a good walker, using your walking feet indoors". You are rewarding your child's specific behavior with your attention and likely increasing that behavior in the future.
Above are a list of compliments you can give your child when they are showing good behavior. Try some of these out with your kids!