Quite a few people already know this: but i'm still gonna say it (or type it).

Take a Pickachu, Clefairy, Psyduck, Pachirisu, Happiny, Buneary or Drifllon into Amity Square (North of Hearthome city) and walk 200 steps. Then face your Pokemon and Press A. You'll get an accessory/berry. You can do this as many times as you like.

PLEASE RATE!!!