One technique of follow-ups are "free narratives." An example of a free-narrative question is, "I have been told you were on the roller coaster when the person near you fell onto the tracks. Could you please describe what happened?" Once you have their answer, then you can follow up with direct questions that occur to you as they provide answers.
A second techinque is "Cross-Questioning." Here, you use multiple questions repeatedly, asking the same information but in different ways. For example, "Did you actually see Ms. Clemmons through the window?" and then later, "Where did you see Miss Clemmons?"
A third method of follow up is "Review Questions." Here, you listen to what the plantiff or suspect has to say, then repeat back his words, in your own words, to assure you have understood the essential information and that it is correct.