How do I become a great GIS specialist?

The best solution is to work more and more in ArcGIS10.1 and reading more about it

Start from zero, so you get the principles that carry your expertises.
I'm here talking about geography (assuming you are ok with IT).
For me nothing helped me like having a GPS devise (Garmin12 - in1999) and play with its data.
Its develop your way to think about vacuum Engineering and Surveying Engineering, so you can know what going on.