Use a text editor that supports colour coding and validates YAML.

Set the text editor encoding to UTF-8.

Do not use tabs. Use only space characters in the YAML syntax.

YAML is case sensitive.

YAML considers that a line indented with more spaces than the section or parameter on the previous line is nested inside that section or parameter in a parent/child relationship. If you want to nest several lines in the same parent section, you should indent all children lines with the same number of spaces.