Update on a schedule
Website software, themes and plugins publish security fixes. Turn on automatic updates where available, and remove plugins you don't use.
Back up and keep a copy elsewhere
A common rule is 3-2-1: three copies, on two kinds of storage, one kept off-site. A backup stored only on the same server can be lost with it.
Test a restore
A backup you've never restored is a guess. Once or twice a year, restore to a test location to make sure it works.
Do this today
Find out how your site is backed up, where the copies live and how to restore one.