Good Luck Wannabe
Remember: Give examples of when you have 'gone the extra mile' and have a good idea what the difference between good and excellent customer service means to you. Be able to talk about the pitfalls, stuff like the unsocial hours, having to work while your mates play at weekends etc., and how you plan to overcome that.
Make up is good as long as its not over the top, smart suit, ( Iv'e interviewed guys in jeans and gals in shorts, got the job? Not!) polished shoes, nice hair and nails. Sounds petty but lot of selection is about how you present yourself. ( Gandmother sucking eggs stuff but you know what I mean)
Also find out a bit about the airline, where they fly, what rosters are like, what aircraft etc. I interviewed a lady last year who had no idea what crew did or what routes my airline flew, indeed she knew nothing about the company, again, no job offer!
Good Luck, be positive and personable and you should be AOK!!