The Deadmines are an instance that most Alliance players are very familiar with. However, with the Cataclysm release the Instance got a make over with new bosses, teleporters, and more. We recently posted a brand new guide for the instance here: The Deadmines, which has now been fully updated to include all the details on how to defeat the bosses in Heroic mode.
This fight revolves mainly around the add tank in the reaper controlling and defeating the adds. If no adds make it to the group, it is a fairly simple fight and easy to win. If an add makes it up the ramp, all but the best groups will wipe. Therefore take your time and explain everything to the add tank and expect a few wipes while they learn the mechanics. Once they understand it though, the fight is cake.