I've never done it but have met people who have and also have a friend who has done it in the past throughout his travels. It has been in the back of my mind for several years now and would definitely like to give it a try sometime. I'm still shady on the best practices on how to do it, tips and tricks, what to look out for, etc. Anybody on here ever done it and know the low down?
http://hitchwiki.org/en/Train_hopping
http://hitchwiki.org/en/Train_hopping