Gather iron pickaxes or better
Bring torches, food, and a water bucket
Go to the Deep Slate layer near Y level -59
Dig a long branch mine or strip mine
Mine at Y level -59 or -58 for best diamond chances
Check caves and ravines at deep levels
Use a Fortune pickaxe to get more diamonds
Use an Iron, Diamond, or Netherite pickaxe to mine diamond ore
Avoid mining with a wooden, stone, or gold pickaxe
Watch for lava and block it with water or blocks
Collect the diamonds and store them safely