Hi there,
I am currently looking to do a PhD. and one of the most harrowing aspect of it, for me, is to find suitable referees. Every application needs two referees and some in Europe and all in the US. need 3. My question is given that my current master through research is supervised by a single PI, where do I get the other two referees from. Many of the post-docs in the group are more than happy to stand in as references for me, but, many of the places I plan to apply in the US. informed me that they, in general they look down on references by post-docs on the suitability of a candidate for a PhD.
An option would be to go back to my Bachelor lecturers, but there again a problem arises with the fact that as lecturers they have not seen me do any research and as such can not comment on my ability in that field.
My question is put to all the students who applied and successfully received PhD. offers in the UK. US. or Europe. Who did you put as your referees and if they didn't directly supervise you how did you approach them to ask for a reference?

Hello...I have just been through this in getting referees for applications, and have been lucky in being successful in getting a PhD so maybe I can send my 2c worth. I think the referees are not necessarily there to see ability in a particular field. Some applications do ask for academic references. For those look at perhaps the head of department where you did your masters (did you help out in demonstrating work they were responsible for, helped organised a seminar...do they know you exist?...try and find someone high up...perhaps an examiner for your MSc, or a collaborator to your supervisor who you have gone to for some queries in your MSc). I did go back to my Bachelor lecturers. Most did not see me do any research, but they could say things about how I ranked in their classes, my English capabilities, how I participated in class, interaction with others.

Alternatively look at perhaps job experiences. I was doing my Masters part time whilst working, so I went to a manager at my job location...my job was not at all related to my PhD studies. But PhD work is much about project and time management, so she discussed how I handled the projects entrusted to me at work, how I worked in a team (yes a PhD is a sole project many times, but it is also team work...you help each other out sometimes, and you must work well in a team). Sometimes I feel that references are not there to see how well you can use a particular technique or so (that is through your CV, and your previous research experience), but they are there to learn a bit more about you...how well do you pick up new techniques/methods, how well can you assess literature, etc

Hope this helps a bit :)