Hey Luis, how are you? Well, it's hard to set a number in the variety of forms that a sentence can present itself. A language is something very mutable, and also there are some poetical arrangements that are not seen as grammatically correct. Sometimes we can change the standard structure to emphasize something, for example: "I looked at her before leaving" and "I did look at her before leaving". In this case, "did" is not neccessary in the second sentence, but it emphasizes the act of looking. If you have further questions, feel free to visit my teaching profile and book a trial lesson. I will be pleased to help you. Bye bye!