If strip-mining is your thing, the best place to mine is at Layer 16 and below, although many believe it’s best to do it between Layers 12 and 16. Layer 16 is the layer where Diamond Ore starts to spawn.
One irritant when digging up or around is when you hit Sand or Gravel. A fast way to get rid of a column of falling Sand/Gravel is to put a Torch under the block. The Torch makes the blocks break automatically.
When mining, keep a Water Bucket with you. If you come across a Lava pool, dump the Water above it to make a walking path.
If you don’t have a Water Bucket—or in general, when mining around a Lava pool, or high in the air—crouch while mining so you don’t fall.