You can find a bunch of them online, all differ significantly and there is no universal way to write a successful admission essay.  Following someone else's essay will not be of much help.  The first thing to do is to convience yourself that you deserve to be in the grad school of your choice.  Write bullet points on why you should be admitted and what qualities will you bring to the department.  This is going to be your selling point and the essence of your essay, once you have these barebones then only explore how other people have articulated similar selling points and before you know you will have a wonderful admission essay.

Hope it helps.