Use Shears to obtain wool from a sheep.

Craft and place a Flower Pot.

Cook and eat a pork chop.

Breed two cows with wheat.

Deal nine hearts of damage in a single hit.

Brew a potion.

Befriend five wolves.

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

Acquire diamonds with your iron tools.

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

Harvest some leather.

Use planks and sticks to make a sword.

Construct a better pickaxe.