How to ask a, probably angry, PhD supervisor for a letter of recommendation after graduation from uni? I was on good terms with my PhD supervisor throughout my studies. After graduation, I gave a talk at a symposium and my PhD supervisor was in the audience. I was planning to add a few sentences of appreciation to my supervisor during my talk, but decided not to (in order to prevent potential awkwardness). After ruminating about the talk, I also noticed that I perhaps took too much credit ("I developed this assay in the past" etc.) and never credited my supervisor once throughout the talk (must have been subconscious, because I don't know why I didn't in hindsight). All of that is true: I developed the experiments on my own and performed them on my own. However, my supervisor has been indispensable when it comes to "meta-knowledge," general guidance and feedback. Overall he seems like one of the nicest professors in our department, so I felt bad. After my talk, he just left the symposium without saying anything to me. Maybe he was in a rush, but I remember he had done it another time in the past, where he was unsatisfied with my performance on a previous talk. Right after the talk, I sent him an appreciation email with candour, but I didn't receive a reply. Over my entire studies, I can only recall a single email of mine that he had ignored. My friend tells me that he was likely busy with travels, but I think it's very likely that he is disappointed for the aforementioned reasons (or another reason I'm not aware of).  

I now need a letter of recommendation from him for my next position. I'm confused on what mode of communication I should opt for (email, phone, in-person) and what content should be communicated. Although in-person seems like the best option, I don't think he is rarely in his office and I live far away now. We are both somewhat socially awkward and averse to awkward tension, so I also feel like a phone conversation might not the right approach. Regarding the content: If I'm apologetic, he might not respond out of awkwardness. There's also the small chance that I'm imagining his anger. If it's just a canned or standard request email, and he is indeed angry at me, he may ignore it or, in the worst - admittedly unlikely - case sabotage the letter of recommendation.  

What mode and content is likely to lead to the best outcome in this situation?
If you were my student, I would fully expect you to take full credit for your work. If I helped you it is good for both of us, but a lot of other people helped your development before we ever met. 

As to the letter of recommendation issue, I would do this in two separate parts, separated by a bit of time. First, make contact and thank him for past help and bring him up to date on your current life/research/whatever. If at all possible, do this in person. I don't know what you mean by a "long way" but a visit back to the university to meet old professors (and thank them) is always fun and worthwhile. If I'm the professor, I will be very happy to see you and hear about your current successes both academic and IRL.

This meeting should give you feedback on his feelings about you, though if you are both a bit awkward, it may be difficult to judge. 

But a bit later, it needn't be long, ask for the letter of recommendation. Your earlier meeting will give you an idea of how formal you need to make the request. Or, if you are completely comfortable in the first meeting, you could do it then, but don't force it. 

As to the answer of aeismail, the video suggestion will work with some people, but not all. If he is a frequent user already then it should be fine. But that, or even a phone call, won't work with everyone (me, for example). In person is best. The more formal the person is, the more important to meet face-to-face, I think. For a generally informal person, first name basis, less formal communication is possible.