I just updated to xcode 5.1 - apple decided to make all apps compile to 64bit by default - My app has some legacy code and I spent the last couple of hours figuring out how to STOP Xcode building for 64bit. Thought this might help people with the same problem...
See the accepted answer for a clearer visual walk thought
(my original text based answer...)
In Targets-->Build Settings-->Architectures-->Architectures
- select other
- delete (press '-') $(ARCH_STANDARD)
- add (press '+') armv7
- add (press '+') armv7s
- clean and build