Hiya. Firstly you need to take your resume and have a good hard look at it- then tailor the crap out of it to suit a retail position! You can make one for department store retail and another for shopfront as well- this shows you are aware of what is needed in the role. Also google position descriptions for the different types of retail stores you are looking at- and talk about HOW you can fit them. Never assume one list of 'relevant experience' fits all. Having looked at alot of resumes over the years (including retail, but have project managed recruitments in a few other similar industries- operational delivery, hospitality, etc) I can honestly say it is always a relief reading a resume and just getting a sense of 'she/he actually understands the job they're applying for! Thank god!
If you sound on paper like you truly understand what the role entails you're halfway there.

Also read company mission statements and prowl their website. If I handed in the same résumé, gave same responses and wore same interview outfit at just jeans and myer it's probably doubtful I'd get both job offers. They're worlds apart in style, consumer target market and company practice.

For retail generally you will wear a similar outfit to the store you are at (eg Myer you would dress more professionally than Cotton On). Black is generally a safe option with a statement piece of jewellery- it shows you are confident but don't need to overdress.

Also apply a couple places you have no interest in working- if you have a trial interview it will get a LOT of jitters out. I find most people fall down on their performance in interview- I always give them feedback of 'treat it as a trial interview for your dream job' and give them a pointer or two if I liked them. Always ask for interview feedback and use it.