I will be staying with a friend in Belo Horizonte and am willing to find a reliable guide who will take us to Ouro Preto for a day tour. Any recommendation ? Thanks 

Hi, pauleiro, if you come up short, it is reasonably simple and completely safe by bus, at least getting there and back. I did it two months ago on my own. The main thing is to have good footwear, as often you have to walk on considerably protruding cobblestone sections. And almost every step you take will involve an up or down change in altitude. I got a tourist map at the bus station and they alerted me the Conceiçao church was closed, but there are other notable ones.

A map is essential unless you have an acute sense of direction. Or location tracking and map on your smartphone. For the town itself, a local guide likely best unless a guide in BHz can demonstrate advanced familiarity. PM me if you wish, though I have not been able to figure out how to add attachments in the PM option.