Ok, seems like no one wants to answer this one so I will have an honest crack at it from a coaches point of view.
In my opinion what makes a good coach has nothing to do with the letters after the name etc. I know coaches that are simply brilliant and are not very good shots and I know a thousand good shots that just couldn`t or can`t coach. I have to say I also know one or two with the letters that are quite frankly, disgracefull.
It`s all to do with whether the coach can communicate to you what they see and can make you understand with ease why you are hopefully hitting the targets. It`s extremely important to explain why you are hitting the targets as it breeds if you like, understanding and confidence into the shooter aswell as make the whole thing interesting. He should not dwell on why you are missing too much but move straight onto how to keep hitting them, keeping your thoughts only positive.
A coach should be calm, confident and collected with a smile and in complete but quiet control. If you find a coach that is arrogant,cocky,loud or such like then walk away. He/she will teach you nothing accept how NOT to address shooting in general and may wind you up so far that you will be put off shooting all together. I have been told quite a few stories of that nature and witnessed one or two myself.
As always, recommendations from good shooters is a good bet to find one and the most expensive is NOT always the best.
On the technical side, the coach must not, repeat, must not forget to use a shotgun. Ha! ha!