Another (small) book that I had almost finished since a while. In theory about teamplay and people management, but really has a general scope.
Title: The One Minute Manager
Author: Kenneth H. Blanchard, Spencer Johnson
The principle is based on three ideas: One minute goals, one minute praising and one minute reprimands.
Those ideas explained a bit more mean "define goals in a quick and concise way", "praise people when they act good and why", and "reprimand when they did bad but only regarding that incorrect action". Of course there are more details or side-actions, like being clear about everything, so for example if you are going to give negative feedback the counterpart knows beforehand you might do it. The base is to be clear, provide fast feedback, do not waste anybody's time and keep going instead of getting stuck in one action (reprisal/praise/whatever).
There are also very nice sentences like "Goals begin behaviors - Consequences maintain behaviors" or "Help people reach their full potential - Catch them doing something right".
We're talking about less than a hundred pages so you can easily read the book in an afternoon.
I recommend it to learn about how to not make anybody waste time. The managing techniques might or might not work, but the primary idea of taking the least of others time is a very nice approach to apply.