I'm moving from Sydney, Australia to San Francisco, CA next week?

As an Australian you'll feel pretty comfortable in California, they're pretty laid back and the fashion is similar for casual wear. Be yourself. Dress how you want to. Americans love Australians so you'll make friends quickly, especially if you're friendly and say hi to your clmates. The weather is chilly in SF proper for most of the year so make sure you have jeans and long sleeves. You can buy cool clothes in SF more inexpensively than at home (no VAT, but about a 9% sales tax). Good luck.