1) Always remember that there are no medications that have no side effects. The only question is whether the side effects are less of a problem than the condition that you are trying to treat. This should underlie all discussions of medication with children.
2) Always point out that we know less about the new medications than we do about the older ones. The phrase, "the devil we know" comes to mind, especially in dealing with methylphenidate and its brothers. The new stuff always looks better, and we almost always find eventually that it is not quite as good as initially advertised.
3) We know less about medications in combination than we do about medications alone. The greater the number of medications we are using on an individual patient, the closer we are moving to experimental medicine. This doesn't mean we shouldn't do it; it does mean that we need to watch carefully, and listen to the parents and children about how these combinations are influencing their lives.
4) Diagnosis in children is fluid. Parents often tell me that "bipolar was ruled out in the eval" or something like that; I usually try (gently) to point out that we actually don't know if this is still true 1 or 2 years later. Kids develop, which is their wonderful strength, but it makes it hard to fit them into neat psychiatric categories. Makes them hard to study.
I liken the use of psychoactive medications in children to a journey in the woods- we have a few well-defined trails (like stimulants and ADHD and SSRIs and depression/anxiety), but a lot of what we do is akin to hiking off the trail. Sometimes you have to do it, especially if you are a family "lost in the woods", but bush-wacking the psychotropic "road less traveled" can be dangerous, and merits full disclosure. The danger of marketing campaigns like the one used for risperdal is that they make us forget that we are actually in uncharted territory.