The principle is the same as Pokéradar chaining, or any chaining method.
All you have to do is keep encountering the same Pokémon over and over again, without scaring one off or encountering a different Pokémon. The more times you encounter the same Pokémon, the higher its level will be, the chances of it having an Egg Move, hold item, perfect IVs or Hidden Ability increase, as well as its chance of being Shiny. Here are some useful tips:
1) Bring Repels – Repels prevent you from encountering wild Pokémon by accident. This is especially useful in caves and while Surfing.
2) Don't break the chain – Encountering another wild Pokémon or letting the Pokémon escape/scaring it off will break the chain. Once in battle, however, you can either catch it, KO it, or run away, it doesn't matter since it doesn't break the chain.
3) Be patient – Even though the chances of finding a Shiny increase with every encounter, there is still no garuntee. Be patient and wait until that Shiny is squirming in your iron grip.
Good luck Shiny hunting!
