Ann Dolin: Phrase is a powerful tool especially when it comes to homework. Research shows that by praising effort rather than intelligence, kids develop greater motivation to keep trying.
So the next time your child brings home a good grade, you did well because you put in that extra study time, instead of you are so smart that's why you got an A.
It's also important to acknowledge even a smallest could good behavior, when it occurs try using that PNP sandwich, positive-negative-positive. Begin with a positive statement followed by a bit of constructive criticism and then end with a positive comment.
For example, I like the way you wrote those sentences so neatly. I see that #3 needs a few more details, but I really love the way you use all these vivid adjectives. And be specific when you are praising your child. Research shows that specific praise is far superior to general complements. Instead of saying, great job, consider saying, I like the way you kept trying even when those problems became harder and don't forget, always start with praise and end with praise.
Keep in mind that using praise to motivate will only work if you stick with it. If you're consistent, praise will begin to be a natural part of the way you interact with your child and positive changes will occur.