My friend, co-podcaster, and co-author, the esteemed educator as well as performer, pianist Kevin Bales, says that to be sure you get your practicing in every day, you should do it the first thing in the morning, before you get swallowed up by other obligations of the day. That’s likely the first part of your practicing process; the rest is how you go about practicing.
Now, how you practice is going to be up to you, though Kevin suggests that part of the process is to tackle a problem you’ve been dealing with, perhaps a particular passage in a song or maybe a technical issue. That seems like a good way to start your practice process or routine. If you take lessons—most of us do even after decades of playing and performing because there’s always something new to learn and the best way to learn something is to study with someone who knows how to teach it—then practicing your assigned lesson is another advisable way to begin your practice session.
I also try to devote at least some time in each practice session to learning new material, a new tune. For a singer, that involves learning lyrics and the melody as it has been written. Whether or not you plan to improvise, you should know the song, the melody and harmonies, the way it was written.
Whatever approach you take, making it a repeatable process makes practicing easier. It also makes committing to sitting down to practice easier because you know what you’re going to work on and how you’re going to approach it. That is, you have a process.