Minecraft wiki entry for Shelters, associated text: It's generally a good idea to put the entrance to your mine inside your shelter, simply so that if you return at night you won't encounter mobs. It's probably a good idea to make sure your mine is well lit by torches, redstone lamps, or glowstone. If playing in a mode besides peaceful, you should put a door so mobs do not get in (use iron doors when on hard - zombies on that difficulty can damage wooden doors to the point of breaking). Buttons are useful for any barrier only opened by Redstone.