Play with the windmills and ride the wind seven times.

Brew a potion.

Stop starvation using Rotten Flesh.

Construct a Dispenser.

Use Shears to obtain wool from a sheep.

Craft and place a sign.

Catch and cook a fish!

Use a saddle to ride a pig, then have the pig get hurt from fall damage while riding it.

Use planks and sticks to make a sword.

Construct a better pickaxe.

Construct one type of each tool (one pickaxe, one spade, one axe and one hoe).

Use planks and sticks to make a pickaxe.