I've seen many conferences talks and I've given some as well. I collected couple tips you may find useful.

Get bright clothes

Yep, I known that you will receive black t-shirt from the conferences stuff. From some reasons they think that software developers love black ones :) However, black stuff doesn't look good on cam. So, try the bright one.

Put shirt into pants

Having business casual shirt put it into pants. This kind of shirt is quite long, having it on the pants optically makes you really short. Ok, if you are really tall guy, 1,95m or more, it doesn't matter, but for the rest of speakers it does. And get a belt.

If you really hate putting a shirt into pants, get t-shirt or better polo shirt. That's also looks good.

Empty your pockets

Many times a conference stuff gives you a clip-on mike - this is a small box. Sometimes they give you two mikes - voice related and camera related ones. Speakers put them into front pockets. That looks really bad. Like big, big something on your loins. Watch this if you are a male - your loins are expected to be narrower than your shoulders - that's the style ;)

So put the mikes boxes into your back pockets or clip them on the belt backwards.

Watch on drinking

There are two reasons I do not recommend drinking during the talk. First that is a funny noise of swallowing when you have mike close to your face. And the second one is that from the audience perspective this is takes quite long when you: open the bottle, get it into you mouth, get a sip or two of water and finally put the bottle on the table. That silence "sounds" awkward.

I am sure that breathing coolly with your nose you will stand one-hour talk without drinking.

Ok, let say that drinking is really critical for you. I give you couple tips:
  • The most important is timing. The audience is supposed not to wait when you're drinking. So prepare a glass first to avoid opening a bottle. Ask the question and drink when someone starts answering. Or say a joke and drink when people are laughing
  • Drink only pure regular water. A juice may tickle a throat and you will start to hack. Sparkling water and beer (God!) are banned. You know belching sounds...blah

Enjoy your speech!

.