Do your homework and become knowledgeable. There is plenty of content on the internet to help you learn about this sport. I like ultrarunning.com and trailrunnermag.com. There are also Facebook groups like TAUR (Trail and Ultra Running) that share a lot of information. Follow these groups and pick up some tips by reading about others experiences. This is also a good place to read about gear reviews and what has or hasn’t worked for others. Get plugged into a local running group and connect with others within these communities that have done ultra’s or are currently in the same journey as you.
Do your homework on the race you are signed up for. Review the course maps and elevation charts, learn where the aid stations are located, find out if crewing is allowed, etc. It can also be helpful to look at pictures from previous years to see some of the terrain. Read others race reports or blogs about the specific race as those usually have real information about the race and what to expect.