• Copy/rename the folder into new name
• Get inside the new folder and rename the .pch and .xcodeproj files. Example rename AppleSample.xcodeproj to MyCoolApp.xcodeproj — and — rename AppleSamplePrefix.pch to MyCoolApp_Prefix.pch
• Delete the build folder. (Using the finder)
• Open .xcodeproj file in text editor, like TextMate or TextWrangler. That’s actually a folder, which contains 4 files (you can also right-click and do Show package contents, which will reveal the files)
• Open project.pbxproj in text editor and replace all instances of the old name with the new name. Be careful not to do a find an replace. Since the default name was AppleSample, there were several references to: AppleSampleAppDelegate.h and AppleSampleAppDelegate.m. You do not want to replace these unless you also rename that file.
• Open .pbxuser where is your user name. Then repeat the previous step by renaming. I’m not sure if this is necessary. You may even be able to delete this file? But changing this file worked for me.
• Load the project file in XCode, do Build/Clean all targets

After following these steps, I was able to open the project and build it to the simulator and the device.

I had one additional problem that I came across later that required a fix. When I finially built the application for “deployment” to the App Store, I had problems signing the code. I complained that it couldn’t find the Certificate for “Scott Anguish”. I looked in the build settings and couldn’t find reference to this name. So again I opened project.pbxproj inside of MyCoolApp.xcodeproj and found 2 instances of this line:

CODE_SIGN_IDENTITY = “Scott Anguish”;

I replaced both of them with the correct code signing identity and it worked!

UPDATE: Check out this bash script which does it for you automatically:
renameXcodeProject.sh