In this message, Amanda gives six quick principles of friendship based on verses in Proverbs:

Principle #1 - Proverbs 16:28, 25:9
Principle #2 - Proverbs 17:9
Principle #3 - Proverbs 18:24
Principle #4 - Proverbs 14:20
Principle #5 - Proverbs 27:9
Principle #6 - Proverbs 22:24-25

Resources mentioned at the end of the sermon:
Books
Relationships: A Mess Worth Making - Tim Lane
Known: Finding Deep Friendships in a Shallow World - Dick and Ruth Foth
Boundaries – Henry Cloud
Keep Your Love On – Danny Silk
Pursuit of God in the Company of Friends – Richard Lamb
Why Can’t We Be Friends - Aimee Byrd
Media
TED Talk: What makes a good life?
Right Now Media - search for studies on relationships