It's an old joke, and the answer is 'from a safe distance'. However, if you're a charity trustee or a company non-exec director trying to exercise your scrutiny function, you often have little option but to do just that. You are reliant, in other words, on what managers and tell you, most often in reports. Getting good at reading between the lines is something you need to do.
The Guardian had a good piece about this the other week. This was written in the light of issues at HSBC which illustrated how easy it was for scrutinisers not to be fully informed by managers, whilst being paid well for it. I have, you will appreciate, no experience of these high finance dealings, but I've sat on a number of charity, NGO and school boards (and still do), and there is one thing that most of this experience tells me – there is a tendency for those who chair such boards to get very close to senior managers – whilst not being paid for it. This is completely understandable, and I make absolutely no claims of corrupt or undue influence. However, to a degree, it means that the scrutiny function has to be carried out not just in relation to senior management, but in terms of the relationship of those managers and the chair of the board.