1. Jachol Cave: look at the dirt patterns and follow the path with most "footprints" - up, down, right, up, left. Use Darius to defeat the boss.
2. Archareon Spire: Use only non-magic characters and slap Gylfi to find the book in the bookcase behind him.
3. He makes a wedding gift when you give him a recipe from Mid at Branch after finding all 20 Memoir Pages.