Craft Eyes of Ender using Ender Pearls and Blaze Powder
Hold an Eye of Ender and use it to make it fly
Follow the direction the Eye of Ender travels
Throw more Eyes of Ender periodically to keep tracking the stronghold
Watch where the Eye of Ender drops back down
Continue moving in the same general direction until the Eye of Ender starts going downward
Dig down carefully when the Eye of Ender hovers or falls straight down
Search underground for the stronghold rooms and corridors
Use multiple Eyes of Ender to confirm the location before digging
Bring torches, food, weapons, and tools before entering the stronghold