- Click on you project, in the left hand organizer.
- Select your target, in the next column over.
- Select the Build Settings tab at the top.
- Scroll down to “Objective-C Automatic Reference Counting” (it may be listed as “CLANG_ENABLE_OBJC_ARC” under the User-Defined settings group),
- and set it to NO.
This is on Xcode 4.2 (Build 4D199).