DO not use coal for torches, make charcoal from 'smelted' tree trucks. Coal is way too valuable to be used as a light source.
If you find lava on the surface write down your coordinates: Lava will come in handy for when my Geothermal Generators are built.
If you decide to be a spelunker and navigate a desert Temple, or jungle Temple, or Mineshaft make sure to place a lot of torches or some sign that you've already cleaned out the place.
Thank you!
-Colin Out