What you need to keep in mind is, if you have found a method that makes you a lot of gold then the best thing to do would be to practice and make it perfect. Once you have figured out a few ways to make gold for WoW, it would be nice to combine those to expand your skills.
A few things you could do is to advertise your instance in trade channel to get low level alts to pay for the instance you are going to run anyway.  You could also collect cloth for an alt that needs it. You would end up looting cloth and coins and every item that is dropped and you can vendor these. Depending on what instance you take you can make quite a bit of gold and more if you get to charging per instance and run it multiple times.