Wow! I could speak at great length on this topic, but I will try to be brief.
There are all different kinds of meetings with all different kinds of expectations during meetings. If you stop reading this answer quickly, then remember this one point. When all else fails, follow the crowd. If you're doing what most everyone else is doing, then you're exercising an extremely safe option during a meeting.
For anyone who has done Agile, during the daily standup EVERYONE is expected to speak and give their status update--what did you do yesterday, what will you do today, address any roadblocks.
If a meeting is a give and take discussion trying to solve a problem, then if you have something to offer, an insight, a suggestion, or whatever, it's a really good idea to speak up with that information.
Some meetings, particularly in front of large groups, can feel like a college professor delivering information to 600 college Freshmen taking Flibertygidjit 101 in which you shut up, take notes, and try to stay awake. I delight in asking at least a question during those meetings, if for no other reason than to ensure everyone is paying attention.
I have been in meetings where someone in a leadership position is all but harping on people to speak and ask questions. Despite this "encouragement", most everyone remains silent because they know that the person leading the meeting really has no interest in our input, and when we open our mouths to speak we will get kicked and beaten, figuratively speaking. This is clearly not a normal, healthy, workplace environment, but most who have been around for a few years can speak to their experiences under these conditions.
In a normal, healthy, workplace environment, you may truly have no input to share during a meeting as you may not know enough about the subject or issue to even form an intelligent question. As such, you may attend meetings about the subject or issue over time, and then one day you may understand enough that a question strikes you so you ask. This is how I attempt to operate. If I don't know enough to ask a question, then why ask a question simply for the sake of appearing awake or interested.