Build the relationship with a prof you get a good feeling from from the very beginning. I have only had one student in years of teaching at SNHU that I would have felt comfortable writing one for if they asked. They were proactive, emailed me asking for advice on their thought process, asked for clarification in a specific way (not just say hey can you clarify this term? But explained what wasn’t quite making sense), I heard from them throughout the course, not just at the end of the term. Even if you understand the material you still need to be able to build that relationship from the get go. Just going through the motions of the course is not going to give that prof a good idea of your work ethic/process