You may have no work experience, but everyone has to start somewhere and if you have interest in one or more musical instruments, the accessories, the students (you could encounter in most stores) music books, instructional materials (CD s/DVD s) and/or specialized drumming, just apply!!!!! Tell them you will start at the bottom. You would be willing to work weekends and holidays and pick up extra shifts so you can obtain on-the-job training as quickly as possible. Above all be confident and go and get em tiger!
You could start by taking in a CV emphasising how enthusiastic you are about music. I doubt you would need too much work experience prior to working in a music store anyway. Good luck!