I guess for me the most important attribute for a TMA-er is possessing the desire to learn more about who our ancestors were, what made them tick, what their day-to-day thoughts and dreams might have been... In this respect I guess the most obvious starting point is the physical remains they left behind in the form of their monuments and hut circles/hillforts etc. One of my joys is to go to these locations - if i can bloody find them, that is - and try to see why they were chosen. Perhaps there are magnetic anonomolies and such like, or perhaps they just shared our appreciation of a good spot. Or perhaps, just perhaps, the maxim that energy cannot be created or destroyed means there are indeed other 'traces' we cannot explain. I don't know.
Whatever, it gets me out in the beautiful countryside, I can try to improve my photography, I might learn something and... hell.. I enjoy it! It would appear many others do, too.