Well I use this mine, tips from friends and adapting it I have found this the best way for me:
Please also note to the left of this would be a mine storage and crafting sort of area.
The larger this area the better, as it gives opportunity for more trunks.
Code:
XXXX XXXX XXXX XXXX XXXX
X X X X X X X X X X
X X X X X X X X X X
X X X X X X X X X X
X X X X X X X X X X
X X X X X X X X X X
X X X X X X X X X X
X X X X X X X X X X
X X X X X X X X X X
X X X X X X X X X X
XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX
XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX
X X X X X X X X X X
X X X X X X X X X X
X X X X X X X X X X
X X X X X X X X X X
X X X X X X X X X X
X X X X X X X X X X
X X X X X X X X X X
X X X X X X X X X X
X X X X X X X X X X
XXXX XXXX XXXX XXXX XXXX
Here's a run-down of the mine:
-That is an example, the X's are the only letters used; they simply represent blocks mined out.
-Everything is 3 blocks high.
-Mining is best for you on level 14 (Y axis) digging 3 up.
-If you choose to you could adapt it to 4 blocks high, this is unnecessary though as it would use more picks and not get you much more than you would with a 3 bloc high mine.
-The entrance (i.e. stairs ladders) are off from the mining hub.
-In a real mine I would have much longer trunks.
-The mining hub is essentially optional, but I would highly recommend it. It is the plate for your chips.
METHOD:
So from your mining hub, which should be 3 blocks high: dig a 2x3 hole in the wall as far out as you like, or if you prefer you could go 4 blocks deeper at a time, which would give you 1 more outward shaft (either side) each time. Now once you have dug that hole a little deeper, it will act as your central trunk for that main shaft. In here dig out in the side wall 1x3 blocks and then go deep 10 blocks, dig right 2 more blocks deeper, and then come back on yourself until you break through to your central shaft again. Then repeat this on the other side of your trunk. Continue to do this all the way along, I like to do this 10 blocks deep in the main trunk and then 'harvest' my mine for any goodies I have come across in the walls.
THEORY:
This mining method is probably the most prosperous way of mining, and it saves smashing up more blocks than you need to, so that means less broken picks and more mining = more diamond = more picks = more diamond...