Stand or Sit?
When you're a part of a group and you need to say something, you may wonder "should I stand up to speak?"
There are several good reasons for standing when you speak:
Your posture is usually better when you stand than when you sit, and it's easier to take a full, deep breath. Consequently, your voice tends to be more powerful when you stand than when you sit.
Even if your voice is no louder when you stand, it carries further when your head is higher than your listener's ears.
Finally, when you're standing and speaking, it's obvious who's in control at that moment. If you're not standing, it's much easier for someone to wrest control from you.
On the other hand, there are some good reasons not to stand up:
If you're at a meeting and no one else stands up when they speak, you run the risk of alienating the other members of the group if you stand up when you speak. Being different is sometimes a good thing, but not always.
If you "seize the reins of authority" by standing up to say something trivial, you can appear pompous and self-important. (For example, standing up to simply say "I agree" is probably unnecessary.)
So when the time comes, you need to compare the risks of drawing attention to yourself to the previously-mentioned benefits of a more powerful voice, and then choose the more effective approach.