Sometimes you want to make a good impression with everyone and seem like you're interested in the rest of the group. Especially when you've just met some new people, it's usually better to lean towards the outgoing end of the scale. Getting that "quiet" label often works against those plans. Here are some simple strategies I came up with that help me be less quiet and come up with things to say:
Tell yourself that you have to say something every so often
One thing that works for me is to make an explicit rule in my head that I have to say something at least every few minutes, preferably more. If not, I know people may perceive me as quiet. It seems basic, but when I spell it out to myself like this, it forces me to continually try to add new points to the discussion. Before realizing this, I'd hang back and listen to everyone, and take everything in, but sometimes go ten minutes or more without uttering a word. Or I'd get lost in my head and get distracted by my own thoughts and daydreams. You can't do that. You have to talk more often than it feels like you do. Consciously knowing this helps you do it.When you're new to a group of people who all know each other, this rule especially applies. The onus is often on you to get yourself into their conversation. They may all be comfortable with each other, and benignly neglect to actively include you.
Don't filter yourself too much when trying to think of something to say
Often when I feel like I can't think of anything to say, there are actually lots of potential conversation topics passing through my mind. But instead of going with them, I nix them for one reason or another; "No, I can't say that. It's too boring.", "No, that's too out of the blue.", "Oh, I'm kind of nervous saying that, though I couldn't tell you why." Instead of censoring yourself too much, just spit out some of the ideas passing through your mind.
Don't fret too much about saying generic things
I've read a lot of advice telling me not to bore people with cliched, unoriginal conversation topics. This has sunk in so much that sometimes I'll find myself paralyzed in social situations. I'll meet someone new and not say anything to them because I think it's a huge faux pas to ask them something uninspired, like where they work.
Just say this stuff anyways. Something is better than nothing. Often, dull questions like, "What do you do for fun?", or "Seen any good movies lately?" get the ball rolling. Soon enough you're talking about something more interesting. They can be a necessary evil, a reliable, if tiresome, fallback. When people ask me questions I've heard to answer a million times before, I'm not always crazy about it, but don't hold it against them either. Ideally you can avoid boring topics, but if you can't think of anything else to say, then go with them as opposed to be quiet.
Take the lead in the conversation if it's not going your way
Often I'll be quiet because the people I'm with are discussing something where I have zero to add, usually because I know nothing about the topic. If that goes on too long, then I'm suddenly the quiet one. If the conversation isn't going your way, try to take the lead and switch it to an area where you'll naturally have more to talk about.More generally, if the other people are talking among themselves, and aren't making an effort to include you, you should take the initiative and try to work your way in there. There's no rule that says you politely have to wait for someone to directly address you and ask your opinion on something.
Sometimes you just can't come up with something to say
These tips continue to help me, but at times my mind draws a blank. When you can't think of something to say, it's often due to shyness and inhibition interfering with your ability to think freely, and reducing these feelings is easier said than done.The other usual explanation is when you honestly have nothing to contribute to the conversation (e.g., everyone is talking about old friends they have in common), and it's not appropriate to try and suddenly change it. But here everyone should at least understand that you can't be expected to be too chatty. Try to say something though when the topic changes.
If you do come off as quiet, do better next time
It's not unusual for someone to be a little tongue-tied around a new group of people. If you do better next time, then people will often forget their first impression of you. They'll realize you aren't a snob after all, or that you aren't meek and boring, and that you're actually a pretty interesting person to have around.