To build a good quality WordPress theme, one must set up the proper development environment including plugins for debugging. The theme code should include key elements like doctype declarations, language attributes, and calling functions like wp_title() and wp_head(). It's important to properly enqueue scripts and styles, register menus and sidebars, validate data for security, and support translations. Themes should also meet accessibility standards regarding headings, ARIA roles, links, controls, and more. Resources for assistance include documentation and Slack support channels.