Angel here!  I had my first real job at the age of 14.  I worked for the Owensboro Family YMCA.  Naturally, I expect my two teenage boys to work so I researched all the places who hire teens.  Here is what I found-->

Make sure that your teen has a resume if possible.  If they have never worked have them get reference letters from teachers, coaches, etc.

Do a mock interview with them.  Prepare them for what to expect.  Have them research the place they are going for an interview.

And most of all GOOD LUCK!