This page will document my default mining technique for Minecraft, which I refer to here as the "One Chunk Branch Mine." It is so named, because its' purpose is to capitalise on the fact that Minecraft's in-game terrain exists as a series of 16 block chunks. This is a systematic method, which allows for the maximum number of diamonds and other resource blocks to be mined, while keeping the non-resource stone in a chunk excavated, to just 45% of the chunk's total area. It is, therefore, exceptionally efficient.
The stone blocks represent stone, with the white blocks representing the blocks that have been mined. The glowstone blocks in the above diagram, actually indicate torches, because the Minecraft Structure Planner did not allow me to place torches. This diagram therefore represents a top down view.
It is important to find the chunk boundaries, which can be displayed by pressing the "F9" key if you have the "Not Enough Items," modification installed. If you do not have this modification, then the co-ordinate display which is visible by pressing the "F3" key within the game will do. Chunk boundaries are indicated by any X or Z co-ordinate, which is cleanly divisible by 16. So 16, 32, 48, 64, 96, 128 and so on.
This mining technique should be first be used at a feet co-ordinate position of 12, on the Y (vertical) axis, and can then be used below that down to bedrock, although you must be careful to avoid lava. It is inefficient to use this method above 16Y, or really to mine above that level at all.
Another advantage of this method, is that once each chunk has been mined out in this manner, with some modifications, each such chunk can be re-used as an underground wheat farm.
Some final calculations:-As mentioned earlier, this method is systematic, and by using it, you may be assured of collecting all possible ore or other resource blocks, within the given chunk.