The standards found in the ANSI (American National Standards Institute) A108.02 document provide the installation method standards used to provide a good looking and long-lasting tile project. When they are followed, the job is headed for success, but when they are not followed, it may be doomed from the beginning.
In the attached photo, it is easy to see the errors that were made resulted in a less than pleasing appearance including lippage, chipped tile, dirt catching areas at the low points, and potential safety issues. We will explore some of the standards.