How to set "selected" in select_tag/options_from_collection_for_select

Assuming that in addition to your @models which contains the full list, you also have @model which contains the current record, then you can do the following:

<%= 
  select_tag "name_dropdown", 
  options_from_collection_for_select(@models, "friendly_id", "name", @model.id) 
%>

Basically, the fourth parameter to options_from_collection_for_select(...) should contain the id of the item you want to be selected. Your second code sample forces the selected id to be 1 every time, and the third sample you posted always makes the first item in @models selected, regardless of the actual currently selected model.