To move a cow you need to think of two things. Pressure and position.
Your body language determines your pressure. Slouch your shoulders, bend down, pick up a blade of grass -- this is low pressure. Stand tall, puff out your chest, wave your arms -- that's high pressure.
To make a cow go where you want, you use just enough pressure from the right position.
The cow thinks through her eyes, so your position in relation to her head is what matters. It's pretty much like a game of pool from there. Position yourself in the right place and exert the right amount of pressure. She will move! Then adjust.
That's about it.