Looking at most textbooks, I found Weinberg's Quantum Theory of Fields to be by far the most superior and I think that's how QFT should be taught as well. I also think the way Weinberg presenting the subject from first principle is the way to make progress in research in fields such as quantum gravity. Recently reading his classic paper on Feynman Rule for Any Spin, I have come to admire his clear vision and ability to create a formalism for a difficult subject like quantum field theory. Unfortunately that doesn't seem to be how quantum field theory is taught in most graduate classes! We really should teach the subject from first principle like we do for special and general relativity. I just like to hear people's opinion on how QFT courses is taught in most places and should be taught.