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1) Don't expect every job to hire you. If you get too confident, you won't get the position.
2) Make sure to be precise on the application form. List all information about yourself; ex: social security no.
3) If you're a minor (under 18 years old) get a work consent form from your school; they won't let you work without one. Also get your parents permission first.
4) Once you get the interview, make sure to dress professionally; in fact, if you take the application home and bring it back, they may give you the interview at that moment. No jeans, no sleeveless tops; and ladies, no really revealing tops or very short skirts.
4a) Most importantly, bring your vital information with you; birth certificate; social security card; state ID (if you live in America) and if you don't have a state ID, GET ONE! That is extremely important. They won't hire you without one.
5) During the interview, make sure not to have your cell phone turned on; maintain eye contact; try to speak without getting nervous
6) most importantly, just relax and be yourself! Have confidence and you'll succeed!
7) Once you get the job, make sure not to bad mouth anybody. Avoid fights, and listen to your superiors, even if you hate them.