ok so first you want to bring a pick axe iron or diamond if you already found some diamond ok so here are the best levels to find diamond(blocks up from bed rock) 4,10 and 16 and start mining it took me 1 hour to find 47 diamonds trust me in mine craft that's not a long time and bring water with you if you fall in lava it can or are mining and you see a diamond but there is lava in your way just dump it on a wall and it will make a path recommend 4 water buckets its hell far down enjoy you diamonds