Personally if I hear a transphobic remark then I will make it clear that such remarks or offensive jokes are not appropriate in the LGBT. I think a lot of transphobia is down to poor understanding and blind insensitivity. Over the summer I am going to work on a leaflet of terms and other educational stuff to have around in coffee hours to improve this. I was thinking about other media, but posters and suchlike would probably be a little insensitive.
I often find myself in discussions about gender and other issues in coffee hours and I always do my best to represent trans people and help educate others about issues surrounding gender that many people haven't even thought much about before. If I keep up a high profile perhaps that will help.
If you can think of anything else I could do that would help please get in contact!