Gil Fronsdal provides a good description of the Buddha’s classical teachings on right speech that you can find at this link: Right Speech
Insight Dialogue is a relational form of Insight Meditation developed by Gregory Kramer and described in his book Insight Dialogue, the Interpersonal Path to Freedom. He describes six guidelines that can help us to explore the power of a meditative approach to speaking and listening in relationship. You can find a brief introduction to those guidelines here: Guidelines
Oren Jay Sofer developed another approach to wise communication that blends mindfulness and Nonviolent Communication. He introduces his approach in this article that focuses on how to stop arguing entitled: How to Stop Arguing