I think it is usually taken from the dormant eye on the flower stalk/spike/whatever.

This is a good website on the subject: http://www.orchideenvermehrung.at/

The above website does tell what media to use, but it really only show how to make one potential new plant out of each node. Friends of mine have made it work, but success rate havn been that high, seems the was problem with strilsation.

But can you actually isolate growth points from a developed flower? I am think differentiated and undifferentiated cells? Would be interesting to hear more. I have heard of root tips turning into new plants. I also once saw a short article about some scientist who claimed to have grow orchids from leaf cuttings, but never saw more than that and I am perhaps to sceptical by nature to beleive all I read…

Gonna be interesting to hear what others have to say, probably more than I could contribute, but I will be listening.