Think of praise (and attention) as you would food. No child should starve from a lack of it, just as no child should become obese from too much of it.

Praise is really proportional to the achievement.

We are all aware that if any criticism is to be given, it must be valuable and lead to change and Improvement. Because of this, we all make the effort to be constructive in our criticism.

In turn, if praise is to be valuable it should be informative, allowing children to build on their achievements.

Praise should go beyond good boy, good girl, well done, that's great, you're wonderful, e.t.c. These “one-size-fits-all'' platitudes are used so often and indiscriminately that for children they have become meaningless and a little confusing.

The teacher tells Mary, who has worked hard all day and made considerable gains in various areas of endeavour, that she's a good girl and has done wonderful work.
Richard has been annoying, rude and destructive for 4 hours. At last, he chooses to behave. Doing no more than sitting in his chair earns a good boy from the teacher. Putting his name at the top of the page earns him terrificand super, along with show me how clever you are and write a bit more.
For Mary the inequity is demoralising and suggests that praise is rarely proportional to the achievement and is frequently inappropriate.

Of course, Mary would rather get something than nothing. The little bit she gets gives her a momentary feel-good, but beyond that, there's not much to hang onto.

Informative praise takes the same, if not more, effort as constructive criticism. Informative praise lets the child know the skills and values they have used.

Angela and Adam your project shows great planning. You have used your time well and fully researched the topic. Congratulations. You must be pleased with the way you worked together. You've cooperated, shared and respected each other's needs. No wonder you look so happy. I'm impressed.

While Informative praise and using more words takes more time, often all that is needed is a simple remark that acknowledges the achievement.
Congratulations. Thank you. That was very difficult.
You did well. I hope you're pleased.
These are preferable to good boy, good girl.

Children respond to their skills and values being recognised and appreciated. With this kind of acknowledgement, children become more informed, self-aware and self-motivated.