First thing I'd suggest is knowing your opponent .. in laymens terms .. ask your girlfriend as much about your parents as you can such as culter attitude and so on .. and past experiences with her last boyfriends that have had the in some cases unfortunante opportunity of meeting them. Once you know what type of people you'll be dealing with you'll be more at ease knowing you can handle what difficulties may come from them.
When meeting your girlfriend's parents what is the first thing you should do?