The key is you need a demarcation token of some sort, and you also just need to be consistent with the format/structure. Every single prompt needs to end with the same keyword so the model knows when the prompt ends and the completion begins.
Alternatively, if you just want to do completions, you still must still with the same format. For instance, for a chatbot, you probably want to include the name of the speaker in the information. Check out the Cornell Movie Dialog Database for an example.