What to say on the phone? please answer?

ok so im a 15 year old student , and i really want a job , my sister has one and shes 14 :L , so i go on google maps and look at the local stores , i call a place that looks suitable , and i find my self stuttering and saying stupid things down the phone to him ,and he hung up on me :L ? what exactly should i say to a complete stranger on the phone when looking for work ??? first answer that's good ill choose as best .