In conversational design, you need to learn linguistics to understand how to write proper prompts. Most automated systems are bad because they speak the way you write. This is because the “designer’ doesn’t have a background in designing for voice.
In voice designing, you still use user-centered design process (personas, usability testing, prototyping, etc.). They’re a little different but you have to if you want a good experience. For example, before designing a dialogue, you need to understand your end-user and their expectation behind using your device. We don’t have wireframes – we have sample dialogues.
Using sample dialogs, write scenarios that your user might use and when writing, use conversational approach. For example, in a typical conversational design, you don’t use “may” since “may” is permissive. How many time have you heard, “You may hang up the call if you are finished. To go back to the main menu, say ‘main menu’” This is not natural, is it? In a conversation, you don’t go back. So how else would you write this? Maybe…”If that’s all you needed, feel free to hang up. For help with anything else, just say ‘help me with something else.”
Another part is contraction. In a conversation, we tend to use contraction (don’t, it’ll, etc.) often. Again, you see this often with automated sys: “It will be created tomorrow”. Replace it with: “No problem. It’ll be done tomorrow”.
Understand that language happens in context. So when designing, keep in mind the context of the user and its device:
User: What’s the weather for today.
Sys: Currently it’s 75 and cloudy.
User: And tomorrow?
Sys: Tomorrow there’ll be thunderstorms with a high of 87 and a low 74.
The area of conversational design is too broad for me to cover in one post but I think I covered some basics.