The articles found in this issue of the Mittellateinisches Jahrbuch (53, 2018) stem from a conference held in Zurich in October 2016. The theme was to discern the role and processes of conscious selection in the medieval transmission of texts. The present introduction surveys basic methodological considerations. First, assessing the dissemination of a text depends on studying manuscripts. Oral transmissions left only indirect testimony. Manuscript transmission was itself subject to considerable losses related to respective types of content, physical packaging, and the use made of the implicated texts and books. (Acts of god were a different matter, and of course a blanket phenomenon with variable but important local consequences.) Changes of medium, including recopying in new types of script and in new forms of assemblage (e.g., joining texts previously transmitted in booklets), likewise caused losses. Merely counting extant manuscripts can mislead and must be complemented by the evidence of textual reception and presence, such as quotations and mentions in early library catalogues. The three processes named in the present title reflect the lessons of the case studies presented at the conference. Collecting texts made for a basis from which selecting occurred, and that selecting sometimes, but not always, promoted the building of a canon.