Whenever you have to give a presentation, it's useful to be able to read a room.If you can grasp the emotional frequency the audience is buzzing at, you're much more likely to be successful in your presentation because you can tailor your delivery to them.
So, how do you read a room?
It's true that an audience as a whole has a vibe or a feeling but you need to remember that it's individuals that make up that audience. As such, what you're really doing is getting a read of individual people and then aggregating that into your perception of the entire room.
How, then, do you read the audience as a whole? Look to an individual person's body language, take it in, and then glance to another. This is best way to read a room fast, as you can get a sense with just a few people of how things are going. If the audience is small enough, try and look to every person every so often. The idea is to get as great a sample of the audience as you can.
While you can certainly pick up a vibe from a room, it's not always as easy to determine the cause of it. If you're giving a presentation, for example, and the reception to your words is feeling frosty and closed off, don't assume straight away that it's something you've done. The audience could have just come from another meeting where some bad news was delivered. Interpreting the actual reason behind a behavioural display is never foolproof.
Don't read too much into things if you don't have evidence of them. If everyone in the room is quiet, it doesn't necessarily mean they're not liking what you're saying - perhaps they've all had a long week.
This leads directly from the previous point - test your hypotheses with your own actions. Running with the example of a frosty reception, you could throw in a light hearted joke to see how the audience reacts. If they perk up, smile or even laugh, that hostile attitude in the beginning may have causes. On the other hand, if the joke falls flat, you get dirty looks or the air in the room hardens even more, you might start lending more weight to the idea that it's you causing the atmosphere.
Getting a solid read on a room before and during a presentation is key to communicating your message clearly and efficiently.