To create a .m and .h file pair to use for shared functions etc

Create Files

Menu > File > New File > Mac OS X > C and C++ > C File

Name it and ensure you change the extension from .c to .m

Add to NewFile.h

#import <UIKit/UIKit.h>

Add import to the .m files that will use it, or to MyAppName_Prefix.pch for all files to include it:

#import "NewFile.h"

Defining Functions

In NewFile.h

void SomeFunctionName();		//Note there is no leading '-'
In NewFile.m

void SomeFunctionName()		//Note there is no leading '-'