I came across a tutorial on Chunk Mining for diamonds. Only one diamond vein will spawn per chunk. This means, obviously, if you find diamonds there won't be anymore in that chunk. Saves lots of time.
Chunks are easy to define. They're a 16x16 block. The x and z coordinates for the edges are divisible by 16. This makes it easy to locate each chunk. You branch mine a chunk on level 10. If you find diamonds then yeh! move to to the next chunk. If not you dig down to level 6 and repeat. Apparently this method gives an 80% chance of finding the diamonds in each chunk if lava, dirt, gravel or a cave hasn't replaced the diamonds in that chunk.
I currently have 4 diamonds (I had almost 30 before I went nuts and made all my armour out of diamonds and made a few pick axes) and 19 blocks of diamond ore (one of my pickaxes has silk touch). Each of those diamond ore blocks can contain up to 4 diamonds. Before this I was only finding a few diamonds a day.
The torches you see on the ground are marking the corners of each chunk.