NSUserDefaultsを使うときはWrapして使うと便利 ref: http://qiita.com/items/2af840ded249b3e4e9bb

Configuration.h

@interface Configuration : NSObject
+ (NSString *)name;
+ (void)setName:(NSString *)value;
+ (BOOL)setting;
+ (void)setSetting:(BOOL)value;
+ (void)synchronize;
@end

Configuration.m

@implementation Configuration
static NSString *CONFIGURATION_NAME = @"Configuration.Name";
+ (NSString *)name {
  NSUserDefaults *userDefaults = [NSUserDefaults standardUserDefaults];
  [userDefaults registerDefaults:@{CONFIGURATION_NAME : @"No Name"}];
  return [userDefaults objectForKey:CONFIGURATION_NAME];
}
+ (void)setName:(NSString *)value {
  NSUserDefaults *userDefaults = [NSUserDefaults standardUserDefaults];
  [userDefaults setObject:value forKey:CONFIGURATION_NAME];
}
static NSString *CONFIGURATION_SETTING = @"Configuration.Setting";
+ (BOOL)setting {
  NSUserDefaults *userDefaults = [NSUserDefaults standardUserDefaults];
  [userDefaults registerDefaults:@{CONFIGURATION_SETTING : @(YES)}];
  return [userDefaults boolForKey:CONFIGURATION_SETTING];
}
+ (void)setSetting:(BOOL)value {
  NSUserDefaults *userDefaults = [NSUserDefaults standardUserDefaults];
  [userDefaults setBool:value forKey:CONFIGURATION_SETTING];
}
+ (void)synchronize {
  [[NSUserDefaults standardUserDefaults] synchronize];
}
@end

Hoge.m

// 設定情報を保存
[Configuration setName:@"Hoge"];
[Configuration setSetting:YES];
[Configuration synchronize];

// 設定情報の読み込み
NSString *name = [Configuration name];
BOOL setting = [Configuration setting];