1. "Buenas tardes" - This is the most common and formal way to say good evening. It is used in most situations, such as when greeting someone you don't know well or when you are in a formal setting.
2. "Buenas noches" - This phrase is used more informally and is typically used when you are greeting someone you know well or when you are in a casual setting.
Both of these phrases can be used to say "good evening" when calling someone, in person, or in writing.