One way I found helpful is to repeat or paraphrase what the other person had said in the conversation. At first I was surprised by how difficult this was. Then I realized it’s because I was just hearing the words but not processing them. This also signifies to the other person that you are understanding and engaging in the conversation.

That's basically it. I find that it serves three functions: one is making the other person feel heard, two is making sure I actually understand what they're saying (misunderstandings are more common than I think!), and three is forcing me to put my own response on hold. That last bit is huge. I had no idea how reactive I was in conversation, and what a detriment it is to communication.

Therapy. :)