When you go to a new place, and there is no one there who knows you from before, simply introduce yourself by the name you want to be called. How did you register for grad schools, with the 'real' name or the 'nickname'?
When we named the kids, we used names that we hoped would not be made into nicknames. That worked for Paul and Clare, though one of Paul's friends calls him Pauly; has since high school! David and Joseph didn't fare as well. Even teachers shorten them to Dave and Joe! Drives me NUTS, but the boys don't seem to mind. Oh well.