I find that the backroom staff gives pretty bad advice for praising/criticizing no matter how good their man management is. They always screw everything up.
As far as what ratings --> what to say, it all depends on the talent level of the player and his attitude. VERY generally, I use these guidelines in the EPL:
6.6 and under = deeply upset
6.6 - 6.8 = disappointed
6.8 - 6.9 = below par
7.0 - 7.4 = acceptable
7.5 - 7.8 = pleased
7.9 and up = delighted
But again these will generally be lower in lower divisions, and you have to figure out how to adjust based on the player.......for instance, twice I've said Mamadou Sahko was playing acceptable when he had around a 7.25 over last five games, and both times he got annoyed and said he wasn't playing well. Obviously his range is all a lot higher.