Few things that you can do if brand new. Get a list of all the configurations, server, sql the memory settings, the database locations where disks are stored..Think of it what happens if this server crashes how do i get it back to what it is now.
How to restore, how to get data back, is it in FULL MODE, SIMPLE MODE what is my disaster plan.
Who has rights to the database, who is backdooring the server, who has sa, change the sa password and secure the puppy...don't let developers on the production box 🙂
Do IOPS check on server...so you know what your boundaries are...what happens at 3 pm does the server die and go slow...
Set up maintenance plans to clear logs, and even set up email to alert you on things CPU high, etc