I presented a basic science project during residency. I am assuming you are a med student that just matched?
The best and most obvious thing I can tell you is to be uber prepared. Know what you are presenting inside and out and back again. Know everything remotely related to what you are presenting. I got peppered with questions and had people question things. You have to be ready to back up your stuff.
Yes it is 10-15 min only and is a powerpoint. Have your PI go over the presentation very well and ask them what questions or issues to expect and what to read up on.
You know folks at ARVO wear shorts and sandels. I would wear dress like you did for interviews, better to be over dressed for something like this
I never had seen anyone getting killed personally but have heard urban legends of it. Just be super prepared and know your stuff.
It was a great experience by the way