Play your recorded dialog multiple times. Each time listen for something different.
1. list new words or phrases, and new constructions
2. list unusual figures of speech, colloquialisms
3. list technical terms.
4. list new proverbs or sayings.
5. play it 1 sentence at a time and transcribe it.
* exercise taken from "Study Skill for Language Students: A Practical Guide", by Sydney G. Donald and Pauline E. Kneale