From a Carnegie Mellon University Professor's Blog

http://vonahn.blogspot.com/2009/12/advice-on-grad-school-applications.html

Quoting a few:
"1. DON'T start your research statement with a quote from Albert Einstein. You may think that's a good idea, but so do the other 50% of the applicants. Hell, don't start it with any quote, unless it's from something like Gossip Girl. XOXO. 

2. DON'T say you've wanted to be a professor since you were 4 years old. We won't believe you. When you were 4, you either wanted to be a policeman, an astronaut, or a firefighter. Admit it."