When resubmitting a paper, should I write individual letters for each reviewer or one common letter?
Usually, you sent back one single letter in which you answer the reviewers questions one by one. I always start with a short note to the editor, listing the major revisions done as bullet points. I also thank the reviewers for their time spent on the review and that their comments advanced my manuscript (of course I write this only if the review really improved my work). Then I start with "Reviewer 1" and list each of his questions or remarks and mark my comments either in bold or in a different color.