Some time ago, I wrote a blog entry called "Three-Person Conversations." Now that I'm writing a book where my main character has three friends, and he's going to parties and public events a lot, I'm finding that I'm revisiting this context, and considering it in terms of multi-character scenes.
These scenes can be disorienting at times for a writer - and if the writer is feeling disoriented, imagine how the reader must feel! My main technique for avoiding confusion (all over my writing) is close point of view. The point of view allows me to provide a single person's understanding of the situation, and to control information by limiting it to that person's perceptions and judgments. Here are some more things to think about as you head into that crowded situation.
1. Consider the entry.
A. Is your character prepared for this situation? Does he/she expect it? What is his/her state of mind? What is his/her purpose in entering?
B. Is your character alone as he/she enters the situation, or does he/she have someone to bring him/her in who will give purpose and direction to their entry?
It's funny, but sometimes when I can't figure out how to get a character to walk into a room cold, I can help myself with the dynamics by giving him another person to walk in with.
2. Consider the character's general impression of the situation.
What does he/she notice first? A particular person, or group of people? An overall impression of chaos? Of bustling activity? Of subdued general chit-chat?
Establishing an initial overall impression of the scene will allow you to set up the general dynamic in the reader's mind; then you can focus on smaller interactions within it, and return to the general dynamic in transitions between those interactions.
3. Consider the drive of smaller interactions.
Is your character's goal the primary thing taking him/her from one interaction to another? Or is your character being buffeted by circumstance from one interaction to another, and trying to stay afloat?
Knowing whether your character or the situation is the primary driver will help you decide how to begin minor interactions and move between them.
4. Consider the dynamic of smaller interactions.
Is your character engaging in one-on-one interactions within the larger situation? What are the conditions under which more people would join each interaction? Interruption? Being brought in by one of the conversation participants? How does your point of view character react to this kind of complexity? Easily, or with some kind of emotional reaction? Are there any times when a single individual gets the attention of the entire group?
5. Within smaller interactions, make sure to consider each participant's motives, background and state of mind.
Even if you're not using other characters' points of view, keeping track of who is interacting and what they want will help you to differentiate between participants, which is especially important when many characters are present.
6. Consider how long each interaction should last.
Is there room within the larger situation for people to have long private conversations? Or does the larger dynamic keep smaller interactions relatively short?
7. Consider how to maintain the reader's awareness, both of the participants in smaller interactions, and of the larger situation.
Is your character aware of things going on outside the interaction in which he/she is engaged? How does that affect his/her engagement in the smaller interaction? Are there people present in the smaller interaction who don't say much but can be noticed in their body language so readers don't forget they are there?
I hope these thoughts give you some ways to analyze those party scenes, playground scenes, ballroom scenes, cocktail lounge scenes, and all the different kinds of multi-character scenes that may present themselves in your writing. I find that thinking these things through can help me improve a scene I've written on gut instinct, or head into a new scene that I'm having trouble starting.
So jump into the group dynamic and have some fun!