custom-enter-title-here.php

<?php
// Change the default Enter Title Here text
function custom_title_here_text( $title ){
     $screen = get_current_screen();
     if  ( 'POST_TYPE' == $screen->post_type ) {
          $title = 'Enter Custom Title';
     }
     return $title;
}
add_filter( 'enter_title_here', 'custom_title_here_text' );
?>