It is very difficult to change their habit unless the guilty start getting punishment. Unfortunately our RTI Act has not yet become that powerful. As you said it is better to resort to methods which can avert such direct confrontation. I resort to speed post even to most of the offices on my way to post oiffice and located within 100 meters from the post office. In very complicated cases where the PIO is likely to deny having received the application I complain to the Post office on non-delivery of the speed post and invariably they intimate the date and time of delivery. After I had resorted to this method thrice, most of the offices I deal with know my habit and no one has denied receipt of my application.