How to lose half of a pound a day?

i would like to lose 3.5 pounds a week, so i need to know how to lose 1/2 pound a day. im 5'1. 121 lbs. I'm 17. female. the amount of calories I'm suppose to have a day to lose weight is 1491 calories. how much should i work off everyday? and what are some things to eat that will speed up my metabolism?