Formal:
* Articulate: To express oneself clearly and effectively.
* Enunciate: To speak clearly and distinctly.
* Orate: To speak formally and eloquently.
* Declaim: To speak in a formal and impassioned way.
* Discourse: To speak or write formally and at length.
* Elucidate: To make something clear and understandable.
Informal:
* Speak eloquently: This is the most direct way to express the idea.
* Express oneself well: This emphasizes the ability to communicate effectively.
* Turn a phrase: This implies skill in using language in a clever or elegant way.
* Hold court: This suggests someone who is charming and persuasive in their speech.
The best verb to use will depend on the specific context and the nuance you want to convey.