SIMPLE & STUPID QUESTION-NEED ANSWER FAST :))

I have a simple question.. I have the iphone 4 and tomorrow I am buying the iphone 5.. what steps do I need to take to insure that my photos, apps, music, contacts, etc will all be saved so I can transfer everything to my new phone tomorrow? I don't want to lose ANYTHING (it has happened before talk about sad day!)...I pretty much want my exact iphone 4 to be on my iphone5 when I buy it. help?!