Going from PC to Mac with iPhone

Google is your friend. Took me 5 seconds to find this

http://www.macworld.com/article/1146958/move_itunes_windows_mac.html

 

Well the above article is quite old (itunes 9!) and I would advice you not to copy over files like that.

A simpler way is to setup iTunes on the Mac and enter your account details and Authorize the computer. Enable Home Sharing on both Mac and PC, then put them on same WiFi network. Once done, on the Mac iTunes, you should see the PC on the left side with subheadings of Apps, Music, etc. You can click each section and copy over to your Mac. This will copy all the stuff from PC to MAC iTunes over WiFi. Simple !

Of course, if you connect your iphone to Mac, you will need to restore everything. It still works the same way

So once everything is copied over. Connect your iphone to Mac, it "may" prompt to setup as new since its synced with another computer (PC)... Do not select that ! On the iphone name on left, Control-Click and Backup the phone. Now setup as new and restore from this backup on the Mac. You are all set !!