A study by Drs John Stoszkowski (@JohnStoszkowski) and Dave Collins (@DaveGM4P) highlights the sources of knowledge for coaches. This full study is available free at the following link currently: http://www.tandfonline.com/doi/full/10.1080/02640414.2015.1072279#.VcSqR3j3Dbw

It was also brilliantly summarised by infographic guru Dr Yann Le Meur of YLMSportScience (@YLMSportScience):

In summary, it seems that most coaches prefer informal learning (as opposed to formal or non-formal) which includes peer discussion, watching other coaches, books and websites, online social networks and YouTube. As study author Dr John Stoszkowski says about the findings in a recent tweet: “Hence [the] need to teach/support coaches to approach info in a critical way in order to make sure self-directed learning optimal“!