how to handle runtime permission auth in android M

I want to know the best practise to ask user for permission check and the code to run if user declines that particular permission access.

This example I copied from http://www.applicoinc.com/blog/android-m-permissions-review/ sets state for the CONTACTS permission:

private static final int PERMISSIONS_REQUEST_READ_CONTACTS = 1;
private static String[] PERMISSIONS_CONTACT =
{Manifest.permission.READ_CONTACTS}   if
(checkSelfPermission(PERMISSIONS_CONTACT)) {    Log.i(TAG,
           "Contact permissions have already been granted. Displaying contact details."); } else {    Log.i(TAG, "Contact permissions has
NOT been granted. Requesting permission.");   
requestPermissions(PERMISSIONS_CONTACT,
PERMISSIONS_REQUEST_READ_CONTACTS); }   …   @Override public void
onRequestPermissionsResult(int requestCode, String[] permissions,
int[] grantResults) {    switch (requestCode) {
       case PERMISSIONS_REQUEST_READ_CONTACTS: {
           if (grantResults[0] == PackageManager.PERMISSION_GRANTED) {
               // permission was granted, yay! do the
               // calendar task you need to do.
               Log.d(TAG, "permission granted");
           } else {
               // permission denied, boo! Disable the
               // functionality that depends on this permission.
               Log.d(TAG, "permission denied");
           }
           return;
       }    } }