By asking friends (all of them, from all walks of your life: from your religious organization, your kids after school activities, your next door neighbor, anywhere youbor your kids are) and posting on neighborhood list servs.

My children over the years have had excellent math tutors, foreign language tutors, and even an Executive Funcrtion Coach. All were recommended by friends from one place or another

I've found good Spanish tutors on Preply, by reading reviews and looking for tutors who are verified as experienced high school teachers. Look for reviews that mention they are organized, competent, efficient instructors who push their students and reviews that mention students improved on exams, not just those who are fun to work with. There is a bit of trial and error though - you may have to try a few before you find someone good.

We have found them by asking on neighborhood listservs for recommendations

If you have an excellent tutor, how did you find him or her? I am struggling to find a good Spanish tutor. I asked the resource teacher at our school and says they no longer maintain a list because of Covid. (This doesn’t make sense of course). I hired one with glowing reviews on Wyzant but my kid received a 2/6 on a grammar assignment she reviewed with her.