I can't tell you where the tilde key is on your keyboard. It depends on which language setting you have your keyboard.

You have to hold the tilde key (~) while clicking on the Hot Spot's shown here.

Hot Spot

Result

Catharine & Yeesha

Look closely at Atrus' writing table. You'll see a lot of cool things on it. The most interesting thing for us is the picture showing his wife Catharine and his daughter Yeesha.

Saavedro's watch

After your first ride with the elevator to the top of the main horn don't return to the bottom after Saavedro's speech. Hold the tilde-key and look again through the window. (You perhaps have to do that twice.)

Hot Spot

Result

Edanna's moth

Deep inside Edanna, go to the "Jumping Dragon" (sort of leaf elevator) there are stairs leading up to it. Go along the side of the stairs then turn to the right and look at the side of the stairs. There's a moth! Now be amazed when it transform itself when you click on it while holding the tilde key.

Spoiler: The cats (Briggs is on the left and Singer's on the right) you see here are the pets of Kelly Standard. She textured whole Edanna.

Headache

After Saavedro steals the Releeshan book and locks the door in the main horn, go up to the window where you can see him walking around. Hold the Tilde-key and look again through the window. (You perhaps have to do that twice.)

Hot Spot

Result

Hammock

There is a nice hammock in Saavedro's lain at the bottom of J'nanin's main horn. But if you look closer near the hammock you'll find something very interesting.

Spoiler: What you see here is a PEZ dispenser (candy). MEB is for Mike Brown (Exile's lead animator). He has a great collection of PEZ dispensers.