Start praising every little step toward the target behavior, making a point of catching the child at being good. Suppose you have told your child he must clean up his toys when he’s through playing with them, though he’s never done this before. Praise every bit of progress, however minor. At first, praise him for picking up one toy even though he’s left three others on the floor. You might say, “It was great the way you picked up your truck and put it in the toy box. Let me help you pick up the others.” The next time, praise him for picking up two items, and so on.