According to a guest on Woman's Hour last week, it's potentially harmful to overpraise your child, telling them everything they do is a work of genius, as apparently they can turn into self-obsessed little snotrags. She gave a delicious example of how to praise without elevating your offspring's ego beyond the moon and stars:
(I paraphrase)
'What a delightful picture, Tallulah, well done! You've worked very hard on that, and I can tell that you wanted to draw a very good princess...' - (under her breath: yeah, you wanted to...but it was shite!!)
Can you think of a good backhanded compliment for someone (young or old, famous or normal) who's worked ever so jolly hard and produced something really, really crap?