Reference: Apple Developer Page

Setup:

1. Create a Single View Application
2. Add two buttons
3. Add a text field
4. Add a label.

NMViewController.h

@interface NMViewController : UIViewController
{
IBOutlet UILabel *label;
IBOutlet UITextField *field;
}
-(IBAction)savedata:(id)sender;
-(IBAction)loaddata:(id)sender;

@end

NMViewController.m

@implementation NMViewController

-(IBAction)savedata:(id)sender;
{
NSString *savestring = field.text;
NSUserDefaults *defaults = [NSUserDefaults standardUserDefaults];
[defaults setObject:savestring forKey:@"savedstring"];
[self.view endEditing:YES];
[defaults synchronize];
}
-(IBAction)loaddata:(id)sender
{
NSUserDefaults *defaults = [NSUserDefaults standardUserDefaults];
NSString *loadstring = [defaults objectForKey:@"savedstring"];
[field setText:loadstring];
[label setText:loadstring];

}
- (void)viewDidLoad
{

[super viewDidLoad];
// Do any additional setup after loading the view, typically from a nib.
[self loaddata:self];
}

- (BOOL)textFieldShouldReturn: (UITextField *)textField
{
[textField resignFirstResponder];
return NO;
}