• Pray before you pick out and send the card.
• Make it brief.
• Tell them how sorry you are for their loss.
• Send a small amount of money if you can.   (Most people don't think about the cost of a funeral.  They are expensive and usually unexpected.  Many times parents haven't prepared financially to bury their children.)

Don't:

• DO NOT Tell them you understand.
• DO NOT Tell them "all things work together for good".  (Although true, they don't want to hear that right now because it brings little comfort in the beginning)
• DO NOT Say anything in the realm of, "It's for the best" or "You can have more kids" or "Things can always be worse" or "Look on the bright side..." or "You need something to take your mind off of things."
• DO NOT Ask them to give you a call if they need anything.  (Put yourself in their place and try to anticipate what they might need.)