remove the {{GAR/link}} from the article talk page
update the {{article history}}, or change the {{GA}} template into article history it when not yet present, like
this diff. This includes adding an action (action=GAR, date= five tildes, link, result= kept or delisted, oldid), and updating currentstatus= DGA for delists.
(delisting only) remove the GA status from WikiProjects banners (setting class= blank is fine)
Article page
(delisting only) remove the good article template from the article
List of good articles
(delisting only) remove the good article from the list of good articles.
Wikipedia:Good articles/all. (figure out the appropriate subpage, there's 15, check the topic= property of {{Article history}})
(community assessment only) If the archive has more than 83 transclusions, it is full. Make a new archive. Increment
Template:GARarchive (if this is still needed).