Minecraft is a deceptively complex game. It is truly great at letting you engage at whatever level makes sense for you. If you just want to put down some blocks and make a colourful pattern, you can do that. If you'd prefer to make a working calculator out of Redstone and tonnes of time, you can even do that.
The game has just got even bigger with the Caves & Cliffs update and plans to get even bigger with the second one later this year. Needless to say, there's even more reason to go Diamond stockpiling. If you want to know how to get them and where to find them, this is what you should know.
How To Mine Diamonds in Minecraft
Before searching for them, you might want to gear up. Not only will you need decent gear to head into the mines but you need an iron pick just to mine them.
Use a Wood Pickaxe to mine Stone, then use the Stone Pickaxe to mine Iron. Smelt the Iron in a furnace and then build yourself an Iron Pickaxe (and probably some Iron armour too). Now you're ready to find those Diamonds.
How To Find Diamonds
Diamonds tend to appear very deep below the ground, reported to be below y=16 or so. Make sure to show your coordinates on-screen by flicking that switch in the settings menu. Alternatively, shift and F3 works on PC. Three numbers should appear on screen and the second one is your Y axis, how far up or down you are.
Go into a mineshaft or cave and look around when below 16. The best way to do this is to get deep and mine out or look for lava. Otherwise, structures like mineshafts and bastions increase your likelihood of finding them but they're inconsistent.
Unfortunately, Diamonds are still quite hard to find and are heavily based on luck but if you do those things, you should be much more likely to find them. Good luck in there