I know a way to find lots of minerals(including diamonds)in minecraft xbox edition.(My results were 27 gold 125 iron 20 diamonds and lots of cobble.)
1.Dig a staircase to bedrock and find the lowest point of bedrock
2.start counting the layers until you get to layer six(the lowest point of bedrock is layer 0)
3.make a long corridor with a little base with crafting tables furnaces and chest just in case you need to empty your inventory or make a new pickaxe.
4.never dig one layer down unless your picking up iron or something then continue making the corridor until you have enough diamonds,gold whatever.
THATS IT hope youre happy with the results like me.XD
Branch mining is the single most efficient form of mining in Minecraft.
What you do is make a that is at least 2x2, it can be 1x1, and make it at least 50 blocks long. Now, at the start of the tunnel, make 1 block wide by 2 block high tunnel branching off of your main tunnel. Then, skip two blocks and make another tunnel of the same dimmensions. You continue this until you reach the end of your main tunnel. Then, you can go down the other wall and do the same.
So if done right, it should look something like this...
This allows you to see all 6 blocks around you in the branching tunnels, up, down, and the two blocks on the left and the right. It is extremely efficient.