Note: If you already have an ipod or iphone with content and want to transfer the songs videos photos etc from your current iPod/iPhone to iTunes so as to sync to the new iphone. Please refer to this guide: http://www.ipodtocomputercopy.com/
Here is the step by step guide shows you how to sync files from old iTunes to new iPhone manually:
Step 1 Connect your new iPhone to your computer and open iTunes.
Step 2 Select your iPhone in the Devices section on the left side of the iTunes window.
Step 3 In the main iTunes browser window, select the Summary.
Step 4 Select the option to "Manually manage music and videos" or "Manually manage music." This will deselect the automatic sync settings for the Music, Movies, and TV Shows tabs. Automatic syncing for Podcasts, Photos, Contacts, and Games can be individually disabled by selecting those options in each of those tabs. Note: When manually managing iPod, disk use is enabled and iPod must always be manually ejected in iTunes before disconnecting it from your computer.
Step 5 Click Apply.
Step 6 To manually add music, audiobooks, movies or TV shows, choose one of these categories under Library on the top-left of the iTunes window.
Step 7 Select and drag items you want (to choose multiple items, Command-click items on a Mac or Control-click items in Windows), then drag them onto your iPod or iPhone icon under Devices.
Step 8 To add a playlist, select it from the left side of the iTunes window and drag it onto your device in the same way.
Step 9 When you are ready to disconnect your iPhone, select it under Devices and click the eject icon next to it.
Done! Enjoy your new iPhone.
More detail: http://www.ipodtocomputercopy.com/