Preparation is awesome! It is really sad when a projector isn't wired correctly, or a laptop battery dies, or a tour guide has to scramble to find materials....
In the classroom:
Schedule a time and date with the arts organization or gallery of your choice. The PCA would love to hear from you
, but a local organization is nice because students have the chance to physically visit and see their completed art. Treat the event like a regular fieldtrip and get the students excited about "going" somewhere.
Do a Skype test call, and not just the automated one that checks your speakers. Actually call and video chat with the arts organization beforehand.
Clear a space on the wall for the video feed to be projected onto, or, if you're lucky enough to have an interactive whiteboard (aka, Smart board or IWB) in your classroom, dust it off because your finally going to try it out (!)
Prepare all art supplies- this requires collaboration between the teacher and the art organization. Make sure both parties know what is going to happen in what amount of time. This is where preparation is REALLY awesome- communication too. Email, phone call, or Skype with the participating organization in advance to get all the specifics covered.