This is a tough one, but I usually just jump around the table. Everyone gets to watch what everyone else is doing. I also normally keep a lot of cards close to my chest though, conduct a lot of my rolls in secret, routinely tweak common creature abilities and stat blocks, adjust common spell effects, so no matter who's watching a scene, no one on the players' side of the table ever fully knows what's up.
For instance, even if one of the spectator players knows the textbook description of the D&D Teleport spell and blurts out that it works on "you and up to 8 willing creatures of your choice within 10 feet" to help another player who split from the party and is off on a scene by themselves, my players now know better than to bet their lives on the book descriptions. There's always an element of unpredictability in my worlds that I add precisely to create drama. I don't want anyone, particularly any low-level player, thinking that they know everything there is to know about kobolds and kobold society simply because they've got the official blurb memorized. As the DM, I create the world. I create the exceptions. The players are allowed educated guessing, where they "think" they know about things, just like I feel we do in real life.