I think you get one every time you sign in, and you get some for answering questions, and you can give one to anybody by just clicking on the orange flower by the question, like I'm going to do for you now. Watch it change to grey, and then it will say +1 (or +1 more than it did before). Did I do a short explanation? What's the matter with me, lol?

marjialexa is correct and no, you don't receive them for purchasing designs and it is not necessary to state when you send them. It's like saying, "way to go, or good question" and you can remain anonymous in who you give them to with the exeception of on the projects page where it shows who "voted" for your project.

here's a flower for you