Instructions
Stand in a large grassy area on any of the Routes. Each Route hides rare Pokemon that can only be found by using the PokeRadar.
Use a Repel item to scare away all of the common Pokemon in the area. Encountering a common Pokemon immediately breaks the chain effect.
Select the PokeRadar option, and tap the lower screen of the DS with your stylus. Select shaking patches of grass.
Run into one of the patches of grass to meet an unusual Pokemon. Capture or defeat the Pokemon to continue the chain. Running from the battle will break the chain.
Walk into another patch of shaking grass. If you encounter a Pokemon of the same species as the first, the chain was successful.