When you are a public speaker, your hands will be your allies if you allow them to participate as co-communicators. They will provide visual evidence that you are present in your body and confident in your thoughts.
However, there are many ways your hands can damage your ability to be an effective speaker. Here they are, in no particular order.
Don't point to a visual with your middle finger.
I once had a client, a Texan, who did this, and when I showed him the video, he said, "Oh my God! I'm flippin' the Chairman the bird." Use your whole hand when pointing, not a single finger. The first finger alone is accusative, the pinky is prissy, and the middle finger is downright hostile.
Avoid clasping your hands behind your back.
We're Americans--we gesture when we speak. There is evidence that doing so helps us find the right words. When Professor William McNeil tied speakers' hands behind their backs, they took longer than usual to find the right words. In other experiments, he found that listeners lost much of the meaning when a speaker's hands were not engaged in talking.
Don't get stuck holding your hands together in front of your tummy.
Okay, you can do it now and then, but if you do it all the time you look like you're protecting yourself, or being a goodie-goodie. It ties up your energy and expressiveness. Dr. David DeSteno has demonstrated that clasping your hands makes you look less trustworthy, and, even more shocking, causes you to behave in a less trustworthy manner.
Don't gesture below the waist.
Your hands should do their speaking on a higher plane, at the level of the gut, the heart, or the head--where they can do their best work, adding passion to your message.
Avoid touching your face, hair or nose.
You will rarely see high level politicians or leaders touch these three anatomical danger zones in front of an audience. Since capturing and holding attention is such a challenge, every word and gesture must align with the message. Scratching an itch, fussing with your hair, or exploring what may or may not be happening in your nose are actions that must be postponed until you are free from the gaze of your public.
Clean your fingernails before you get on stage.
Then leave them alone. It is interesting that conversing with a circle of friends is easier when our hands are busy. Card playing and quilting bees are two cases in point. But your listeners interpret every gesture, and the only interpretations they could possibly have of your public self-manicure are, that 1.) you have dirty fingernails, or 2.) you're not all that interested in what you're talking about. Anyway, personal hygiene is a private affair.
Don't make squirrel paws.
When I was a very young child, my uncle took me to the Central Park Zoo to feed peanuts to squirrels. The squirrels were tame, and stood on their hind legs with their paws hanging in front of their chests. I see speakers with squirrel paws--limp hands, devoid of life--and no matter how bright the speaker, I am not impressed. A squirrel-paw speaker doesn't look like he can get anything done. Pump energy and life into your hands to demonstrate your bias for action.
Leave your wedding ring alone.
I see people who appear to be trying to twist it off. The late & great Christopher Hitchens said, "If you can give a decent speech in public or cut any kind of figure on the podium, then you never need dine or sleep alone." If you are twisting your rings, I am going to assume that you have no need for random dinner partners or overnight guests, and that you are simply nervous.
I suggest you put that energy to better purpose by recruiting your hands to put life and energy into your speech or presentation.