Parenting
The best thing I ever heard said about parenting was: "Everyone who comes to this world brings a gift to this world, and a parent can help the person sort out what it is."
Just a single sentence, but following through with the implications would probably be better than the advice of some entire books. For example doing enough with a child to get an understanding of what the kid's gifts could possibly be.
Something related that seems important to me, don't worry if the kid isn't Einstein the second. I know someone who is not the brightest. He would be the first to admit it, but he is pleasant to be around.
He is a nice contrast to some intelligent people I know whose intelligence mostly goes into helping out their greed or their argument skills. Some of them I would be really happy to cross the street to not even have to bother saying "hi" to them.
Once in awhile when they are displaying their nasty side, "you must have a lot of people who really love you" seems like an appropriate comment, sarcastic of course.
There seems to be a random wild card in genes and attitudes, and any kid might not have the rest of the family's obvious intelligence. 
Understanding about life and the human heart isn't necessarily related to IQ. Some people are not the brightest and there is a limit to what they can do about it, but that doesn't mean that they can't have a pleasant, enjoyable, useful, and beautiful life.
