Let them have the serve regardless of who scores. Score more points to win a game.
Personally, when I'm playing a new player who is not yet interested, I play a less structured game. I do passes and shots that are lower percentage but flashy. It shows them what possible without blowing them off the table.
Also, if there are 3 of y'all, play cutthroat. One plays singles the other two play doubles and rotate every point or game. Always fun for newbies because they get to play with a better player every few games.