I have been doing a lot of work this year with 2nd years students at my course Communication and Multimedia Design in Rotterdam regarding wireframing together with my colleague Joel Laumans. Part of it was a wireframing workshop we presented, a document with some details on what a wireframe should contain and a few presentations. To accompany this, I have written an Howto document that you can printout. It also accompanies a zip file where a very simple wireframe can be found that you may download to play around with.
Download them both here: