Use a legitimate texture pack or brightness settings to improve visibility in caves
Strip mine at the correct Y-level for the ore you want
Explore deep caves and ravines where ores are exposed naturally
Use Night Vision potions to spot ores more easily
Use F3 or debug info to track coordinates while mining
Place torches or other light sources to reveal hidden areas
Use a resource pack that highlights specific blocks if allowed on your server
Ask server staff for permitted mining tools or mods if you are on a multiplayer server