The young, having suffered fewer losses, are the worst at condolences.
Case in point: A funeral for young woman who killed herself. After the service, the deceased woman's friends talked with the distraught mother. One girl, obviously a sweet person, but unacquainted with death, made a mild joke, intended to break a tension that could not be broken. The mother reacted angrily, instantly teaching the girl a lesson about mourning she likely never forgot.
What should you say when a well-meaning young person says just the wrong thing?
* Walk away. If you can muster the words, make a polite exit. If not, just walk. Lesson taught.
* Teach. Say "Now is not the right time." and excuse yourself.
* Respond kindly. In one case a young man consoled a wife who lost her husband to Alzheimer's. She had been her husband's caretaker for many years. The young man said that at least she wouldn't have the burden of care. The wife responded kindly: I liked caring for him. It was a labor of love. Then she walked away.
If, as an elder, you have the occasion to instruct a young person before they get to a funeral, do so.
Most young people should be instructed to say "I am so sorry" followed by a hug and no other word.
This avoids the major errors of consolation we so often see. According to the New York Times, the worst thing anyone can do is compare their feelings to the grieved party: I know how you feel. Well, no you don't. Or, I cried all night. Really? I am pretty sure I feel worse.