1) Go outside
2) Dig out some dirt
3) Make a cube out of that dirt
4) (optional) Build a house, kill things and make stuff out of them, flood your house with water, dig a huge mine in your own backyard, dig under sand and have it collapse on top of you, make glass out of sand!
5) IRL Minecraft! (minus night monsters)

(Replace "dirt" with any other solid material for bonus points!)

ALSO:

1) Dig out some diamonds.
2) Die soon after without getting a chance to put them somewhere safe.