Before you go inside of a wall, you should make a small square
hole which you could think it a cave, surround it and put some torches on the
wall. Now you filling this cave with few things like a bed, a crafting table
and a chest. You’ll put resources that you get here during the mining. Then you
could start your journey, mining some resources such as iron ore, gold, diamond
or flint.
One thing I want you to remember that during the journey,
just keep mining straight, unless you don’t hit anything then change the
direction, it will open the new parts of the mine. Once you find the resource,
get a lot of it and come back your bat cave to make some things like armors,
sword diamond/iron ingot.