2) Oh WOW! How exciting!
3) You'll be wonderful parents- what a lucky child!
4) Tell me more about it!
5) That's great- I can't wait to meet them!
Things NOT to say to your friend when they say they are adopting (not that you aren't well-meaning...):
1) I'll still be praying for you to have your own.
2) Maybe this will take the pressure off and then you can finally get pregnant!
4) Oh, well... at least you can still have a family this way...
5) Have you talked to _(insert name of family with horrific adoption experience here)_ ? You might want to before you make up your mind.