Taking the time to think about what you value, what you are interested in and what you are good at doing will allow you to identify the best kinds of job roles and environments -- and make the application process so much easier. You will find this self-knowledge helpful for both informational and regular interviewing, and you can continue to adjust your reflections over the course of your career. Once you evaluate and understand your skills and strengths, and throw in some thinking about your personal and work values , you are better equipped to determine which career paths will be the best fit for you and where you will find the greatest success.
Not just humor, but the overall tone of your application essay is remarkably important. It's also difficult to get right. When you are asked to write about your accomplishments, those 750 words on how great you are can make you sound like a braggart. Be careful to balance your pride in your achievements with humility and generosity towards others. You also want to avoid sounding like a whiner -- use your essay to show off your skills, not to explain the injustices that lead to your low math score or failure to graduate #1 in your class.