I wanted to pull a couple of things from the comments to my post on supporting family members who are adopting. A number of people made similar remarks and as soon as I read them, I was slapping my forehead saying, "How could I have left that off?" That's what I get for writing after midnight. Like I am right now. Ahem.
A theme quickly emerged in the comments: respect.
Respect our decision-making process
It never fails. Anyone adopting domestically gets told, "You should go international." Anyone adopting internationally gets asked, "Why not adopt a kid here at home?" People choosing out of fertility treatments get encouraged to "try this procedure I saw on Oprah" and those choosing treatments get asked why they don't "just adopt." You may think you're offering a much-needed piece of advice. But unless asked, don't offer. There are many, many choices we each face on our paths to parenthood. Trust that we've considered them and know what is best for us in this moment.
You rarely know someone's whole story. And the parts you don't know are often more important than the ones you do.
Respect the other triad members
A number of commenters brought this up, and I completely agree. There is no such thing as an isolated individual in adoption. The child your family members will adopt already has a history and identity--even if he is an infant. She has a family of origin and perhaps another country of origin. Speak positively of those people and places. Respect the privacy of her adoption story by not prying for details and not sharing the ones you know.
Also, the first family members. Birth families are not mysterious folk--they are regular people you likely meet every day without knowing it. The stereotypes about them in popular media are pretty absurd. Any assumption you make about them is likely to be wrong. If you're lucky enough to be part of an open adoption, take the time to learn about them as full-fledged people, not just characters in your family members' adoption stories. In closed adoptions, acknowledge their importance in the child's history. Use positive language and respect their privacy (you would not believe the personal questions people ask me about my kids' first parents that they would never normally ask). Even in more difficult situations, such as cases of abuse, remember that they are still the child's biological family and kids will absorb any comments you make about their first family as comments about themselves. It's possible to be honest without demonizing or insulting.