Toss the ball to the service hit spot for them. Let them cock the racquet
and just hit. Once they understand and feel the proper service hit spot,
then they can add the other first part of the serve (or the toss to the
hit spot).
I taught a lesson called “Learn the second serve first.” Simply stated, a
player is as strong as her weakest link, and the weakest link in tennis is the
second serve. The clue is Welby Van Horn’s balance technique. I call it the
“hit-turn” serve and it came from limited foot movement. It’s also called a
ballistic swing and baseballers, golfers, and all “hitters” use this technique.
Van Horn is worth studying, and I appreciated the personal help he
gave me.

2. The backhand is tough for beginners. It becomes much easier if you are in the correct position.

Give the newcomer a ball. Have them start with the racket in the proper backswing position with the proper grip. Righthanders toss themselves the ball softly and slightly in front of themselves. Toss the ball lefthanded and underhanded over the low backswing, Step properly with your right foot and “lift a descending ball in the perfect HIT-SPOT. Once a player experiences how the proper contact moment feels, progress follows.