The first really helpful book I read many years ago was The Digital Photography Book by Scott Kelby. It’s very basic but he covers a lot of simple things that people often overlook.
One is not to shoot down on flowers. He claims that this will produce a boring shot because people are used to seeing flowers this way, so get down and dirty with them: “well, at least your knees anyway,” says the merry prankster.
He may be right, he may be crazy, but he overlooks a very important part of the photographer/flower interaction. If you look down on flowers they sense the condescension. How is that a problem you might ask?
Once they get the feeling that you think you’re better than them they will mess up your photos every time. Even on the calmest day, a day that’s as calm as a convent they will move just enough to blur the shot, especially closeups.
If you use a tripod and the self timer they have you by the stamens, because then they know exactly when to shake it off. It may sound crazy but I’ve seen it over and over again.
The Buddha allegedly said that if we could see the miracle of a single flower clearly, our whole life would change. You might want to mention that to them right from the beginning.