I admit I'm not really good in including description in the dialogue. I tend to write just the dialogue first, that's my first instinct. And then I add the other stuff. Because, although I believe that less is more, there should be enough description that the reader is still in the situation, not in some sort of bubble.

He said/she said - that's a habit I don't have, for the simple reason that the German "er/sie sagte" doesn't slip as easily into a text than the english variant. It's more or less the first thing we get drilled in us when we start to do writing assignements: use alternative words. There is a little bit more choice in German than in englisch, but it's ingrained in me to look for alternatives "he questioned, answered, whispered, shouted, assumed, suspected, quoted, injected, opted, voiced aso.

Otherwise it depends on the narration. If the scene is written from the pov of one person, said person can watch the reactions of the other persons and trying to read them. (it's also fun to switch pov and it turns out that the reading was totally wrong). But in general, it always helps to let the people do something. Drinking or eating, having something in the hand they play with, whatever fits the situation.

But I think, you can easily get away with keeping at least part of the dialogue just dialogue between two persons, you just have to pay attention that it's obvious who said what and that the passage isn't too long.