Breed two cows with wheat.

Smelt Wood Trunks using Charcoal to make more Charcoal.

Relieve a Blaze of its rod.

Destroy a Ghast with a fireball.

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

Catch and cook a fish!

Play a music disc in a Jukebox.

Wear a full suit of Iron Armour.

Turn wheat into bread.

Attack and destroy a monster.

Harvest some leather.

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

Use planks and sticks to make a pickaxe.