You'll need to build housing (and fulfill other requirements) in order for helpful NPCs to arrive. An acceptable house needs a floor, ceiling, and walls on the sides, along with a back wall, a table, a chair, and some lighting.
Published:Caption:Jason ParkerPhoto:Screenshot by Jason Parker/CNET
Using the zoom window
As you dig down, you'll come across large caverns you can explore. When you find a vein of ore to mine, a small window zooms in on the action so you can select specific blocks to hit with your pickaxe.