Uggggh... this doesn't make any sense :( I have a Magneton with Magnet Pull yet I'm getting more Rhyhorn and Vibrava. All of the grass moves in exactly the same way, too- not that I could tell. The effect doesn't last long enough for me to find the shaking grass either. Does anyone know what I could be doing wrong?
As for the grass you'll have to have a sharp eye. I usually go in the grass that doesn't sparkle white at first, and then continue to go in those patches until I see a shiny patch. You probably want the poketch app telling you your chain. The rule of thumb is to stop at 40, which may be hard to achieve, which is why it takes patience. When going into a patch, like synerjee said, I step in the one farthest from me thats not on an edge or corner. And never be afraid to reset the radar. If you see a lot of patches really close to you or anything run around a little so you can reset the radar.
The shiny patch will not be the white shining patches, but the red/pink glowing ones.