Don't get into arguments. If a person lies, he or she lies. Avoid repetition If you are a defendant, you have the right to call the plaintiff as your witness, albeit a hostile one, after he or she concludes his or her testimony. If you do so, do not repeat questions on cross-examination. The arbitrator or judge got the point the first time it was made.
Judges hate repetition more than anything.
They feel it wastes their time. Sometimes, though, it is useful to be repetitive if you keep it brief. If there is a common theme, you may use that as well to some extent. You asked the person for the money, in front of witnesses, and she acknowledged the debt but said that she couldn't pay you right away. Then you saw her in the supermarket and asked her about it, and she said that she was planning on writing a check to you tomorrow, and wouldn't forget it.