What are the subjunctive triggers?

A good acronym to remember is WEIRDO, standing for wishes, emotions, impersonal expressions, recommendations, doubt and ojalá. For example, espero que, dudo que, estoy contenta que, es importante que, recomiendo que, dudo que y olajá que no llueva. Remembering this acronym makes it easier to remember the subjunctive triggers which sometimes can be difficult as there are many!