@ i would look over the apple support forums for ways to solve common apple errors (like how to manually reboot an ipod when it freezes, etc.) . If possible go to the store and have a friendly conversation with any employees (most ppl are usually friendly and there are lots of conversation starters). As for specific programs, iLife has a lot of “how do i this” questions, definitely iTunes, how to change user preferences, (unless you are applying as an apple trainer, you dont need to know the details of specific programs like final cut pro). Instead of programs, the major thing you should think about is trouble-shooting errors – most of them are pretty simple – some of them you’ll know already – if you dont how to solve a problem, google it
Btw i dont it it helps or not but i wore a DIGGnation shirt on my interview day which ( as my retired manager jeff describes it) gave them the “pure geek” impression