What most naturally follows?

How to get a hydreigon in pokémon black 
Go to victory road. 
You must first catch a deino, which can be found on the 1st and 3rd floors of victory road by walking, and it has a 20% of showing up. The location of deino is the same in both black and white.
Carry a pokémon with you that has status-affecting moves such as thunder wave or hypnosis. It would also be wise to have a pokémon who knows the move false swipe.