HufflePicket asks: I have a bunch of characters who don't know each other very well. They're sort of meeting in groups of two or three, but I don't really know how to write introductions or get them to know each other. Any advice?
Keep Formalities to Formal Occasions
It may be tempting to get such introductions out of the way by one character formally (and stiffly) saying, "This is Charlie and Robin, and they are explosives experts." Unless the occasion is formal (like a dinner party or teacher's conference) we want to avoid being formal all the time. Once in a while is fine.
Just think about real life situations. When you bring a friend home for the first time, you will likely sound formal. "Mom, this is Billy. We're studying together." The level of formality is highly dependent on the situation. When the purpose of the occasion is to meet people, introductions will tend to be structured and boring, but necessary.
Natural Dialogue
In the situation that HufflePicket brings up, it seems that these characters might be thrown together as circumstances arise. In these cases, it's important for you to fire up that movie projector in your head and imagine how such a scenario might play out.
You must first have a good sense of each character's personality. Each one will react to the same situation differently. Let's say two teams who have never met rendezvous at a checkpoint and have to coordinate the next move. Think about how each personality handles such a situation. Here's an example:
Sam (friendly and loves meeting new people): Hi! I'm Sam. Glad you guys made it.
Jane (aggressive and likes to take control): Right. We don't have much time. Did you bring the software?
Brent (has problems with authority and dislikes aggressive people): Hello to you too. Of course we brought it.
Sam: Brent is our hacker. He's very good.
Jane: Great. We brought our own. Wanda?
Wanda (wary and mistrusting): *says nothing but makes a sour face at being singled out*
In scenes like this, the introductions should feel like a natural ebb and flow of dialogue. In my short example here, the two most socially outgoing people dominate the conversation, as such people tend to do in real life. Some characters will introduce themselves. Others are happy to let others do it for them. Still other may prefer not to be there at all. Put yourself into the shoes of each character and have them react accordingly. This is a great way to handle new characters meeting each other for the first time.
Let It Unfold
Don't feel the need to push information about all the characters to the reader. Let it unfold naturally. Like in real life, we will gradually get to know some people sooner than others. Those who are more guarded will take more time to get to know. Treat it like a friendship, not a research paper. If it feels forced when you write it, then you might be pushing. Ease up and let things unfold at each character's individual pace.