Authors want to manipulate readers' thoughts — this is why we read, after all. We love getting swept away into new worlds, with new people and ideas. Getting a reader's thought map is a great way to hone this skill.
When writing phone conversations, does your one-sided dialogue give insight into the character of one or both participants or the relationship between them? Is the conversation moving the plot forward?
Mind mapping is a technique for outlining information in diagrams using written text as well as lines, symbols, keywords, colors, and images.