It helped me really iron out what mattered to me in terms of birth - what I wanted, my priorities, and how I wanted both my partner and I to be treated / spoken to - and my midwives really took it on board. This included when I had to have an emergency c-section; I only included a small part on this as was hoping for a vaginal birth but they took it seriously and followed my requests. There’s a good NHS template you can follow and just whittle down to what actually matters so it’s quick and easy for them to follow.
I recommend looking up a birth plan with a modifier (i.e. “Natural Birth Plan” or “Hospital Birth Plan”). Then research each thing or at least google what it means, and use that as a guide 😊 People have posted tons of birth plan templates etc in the blog/IG universe
It's basically your preferences. For example I like minimal intervention and least restrictions. Which meant delayed epidural so I can move as desired.