After beating the Elite Four and Stark Mt., go to the mansion south of Hearthrome. The owner of the mansion, in the office, will refer to pokemon in his garden. After a scuffle with the butler, you can go into the garden and catch the pokemon he referred to. Use a Quick Ball for an easy catch. You can do this every day for a new pokemon!
This article uses material from the IGN and is licensed under the Creative Commons Attribution-ShareAlike License