About Mattj's method with the shaking ground or grass to confirm your seed. . . where a shaking patch will appear is also based on your walking pattern. I hit my seed around 7 times for my Kyurem, walked different paths each time, and the shaking patch appeared in different locations. One of the times it appeared directly under me. :( However, the last two times it did appear in the same spot. So I would recommend walking the entire length of the map one way and back until the shaking patch appears.