I found that sometimes its how and when you give in your CV that can make a difference to whether you get a job or not. For example, April/May is the best time to apply for jobs.
Also don't hand in your CV to some other sales assistant in the shop, don't post it in and don't just leave it on a desk. Go and give it to the person in charge, literally place it in their hands and show them your face. Sounds stupid, but so many people aged 16 just hand in their CV to anyone, hoping it will get to the manager/boss. 80% of the time it won't. Be well dressed and hand it into the person who is in charge. They will remember it compared to just receiving it from the parent of a child, or just finding it on the desk.
Also after handing it, wait 10-12 days, and call the place, asking to speak to the manager/boss. Ask them whether they have had a chance to see your CV and when you will hear back. This makes it clear to them that you actually want the job, plus its given them a second chance to hear you/see you, therefore they are more likely to remember you.
Good luck!