Preachers often start with a text, but then jump to five to ten other texts to support the point of their text. This distracts, distorts, and dilutes focus on the text at hand.
Every text conveys main-line information and support information. The most important material an author wants to communicate is expressed in the main-line material. Support material is secondary.
What we are about in Text-Driven preaching is helping preachers understand the semantic structure of their text; especially so they can clearly identify the main-line information vs. the support information. Then they can structure their sermon according to the actual structure of the text such that the author's main points and subordinate points are carefully expressed. This is how meaning is clarified.
The Bible is written in different genres. Preaching should respect and reflect these genres in terms of sermon structure. Every text conveys a certain tone or feel. This should be reflected in the sermon as well.