Handling dialogue for more than two characters When you have more than two characters in a scene, you have to be careful that you don't leave anyone out for longer than three or four lines. Think of the scene as you would real life. You would not talk exclusively to Jill if Gwen were sitting beside her. You might be wanting to prove that Gwen is of no account and therefore the point of your conversation is to exclude her. If that's the case, you have to let the reader know what you're doing.
Some scenes require one or more additional people around at the beginning.
However if you want to have any personal conversation between two of your characters, you're going to have to get the others to leave or move your people away from the group. In my book Grey Fox Wagers, Jena is accompanied by Nanny to find toe drunken peg-legged Martine. I needed Nanny for convention's sake and wanted her to do some things in the room before Jena's talk with Martine. It's a shouting scene which would be awkward with a third person having to be catered to. Jena offers Nanny a cup of tea.