Hello there. I'm attending an introductory course in particle physics. We're supposed to know how to draw first-order tree level Feynman diagrams for simple reactions. I've been struggling to understand the method I should follow in order to correctly draw them. As I understand it now, we can combine the elementary vertexes of each interaction to get any possible diagram. Starting from what I've learned by reading Griffiths' book and from my classes, I tried to write some notes about this, and found out that I have some unanswered questions about it. I attached my pdf file with my notes, with the questions clearly identified in boxes - everything inside a box is a question. If you could please answer some of those and perhaps see if I got the concepts right, I'd be very grateful.