Once you have developed a sense of the faculty's interests and the department's special features, you can make it clear in your application exactly why you want to attend that particular school. What is it about the department's curriculum structure or general approach to the field that makes you interested in being a student there? Don't waste your valuable essay space, or your reader's valuable time, telling the reader how wonderful or prestigious their institution is; people on the admissions committee already know this. They want to know about you.
Do tie yourself to the college. Be specific about what this particular school can do for you. Your essay can have different slants for different colleges.
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Do tell the truth about yourself. The admission committee is anonymous to you; you are completely unknown to it. Even if you run into a committee member in the future, he will have no way of connecting your essay (out of the thousands he has read) to you.