#if __IPHONE_OS_VERSION_MAX_ALLOWED >= 80000
if ([application respondsToSelector:@selector(registerUserNotificationSettings:)]) {
    // use registerUserNotificationSettings
} else {
    // use registerForRemoteNotifications
}
#else
// use registerForRemoteNotifications
#endif
If you are only using Xcode 6 (beta), you can stick with just this:
if ([application respondsToSelector:@selector(registerUserNotificationSettings:)]) {
    // use registerUserNotificationSettings
} else {
    // use registerForRemoteNotifications
}

registerForRemoteNotificationTypes: is not supported in iOS 8.0 and later