Google Sheets is the author's preferred to-do list app due to its customizability, minimal clicks required, and existing use of the tool for other purposes. The author has created a Google Sheets template for using as a to-do list, which includes three main columns: Day (when to do it), Tasks (what to do), and Notes/Links (other stuff). The spreadsheet can be customized with additional columns such as Task type and Time estimate, and formatting options like conditional formatting. The author uses Zapier to automate tasks, such as sending messages from Slack to the Google Sheets to-do list. Once a task is completed, it can be marked off by striking through the row or using checkboxes. To keep the to-do list manageable, previous weeks' rows can be hidden.