The Arnie Schwarzenegger Approach is the best way to go for the baby set
For the very young set (birth to puberty), I would strongly favor the exercise and drill approach—not physical but mental, of course.
We have discussed how an integral part of the neural growth process is stimulation.
We have seen evidence of retarded brain growth in Rumanian orphans who have been relatively deprived of stimulation.
We know that stimulating the young brain brings very large gains. In other words we know what to do and when to do it! Now comes the how.
Any activity that exercises memory in the infant is worth its weight in gold.