Before you upgrade to the new iPhone 4S or upgrade to the new IOS 5 you absolutely need to make sure you backup your data before you move to the new phone or version of the iPhone OS or you may lose valuable data, apps or contacts!
This Lifehacker article will guide you through backing up your data.
Once you have this completed, you're ready to move to that new iPhone 4S or update to IOS5.
But with all that's new inside IOS5, there are quite a bit of items that need setup for iCloud and this Lifehacker article will help you set all those new features up.
And then you can go exploring some of the hundreds of new features. But this Wired article will help you find 7 of the hidden gems.