Googling for this error didn't turn up any useful matches so I figured I'd share the knowledge:

If you just installed Redmine and you get this error the first time you attempt to serve a web page:

Table 'redmine_development.settings' doesn't exist: SHOW FIELDS FROM `settings`

You forgot the essential but simple step of bootstrapping the database. Run:

rake db:migrate RAILS_ENV="production"
rake redmine:load_default_data RAILS_ENV="production"

And maybe restart your server? That should fix it.