I have been doing them for a while and it has become part of my job role. I really just practice them over and over. If I am feeling confident I will practice a presentation three or four times. If not it is closer to ten times with lots of edits. When I present I try to tell a story and by practicing I am really clear on what I want my talking points are and how I want to say it. When I present I often go into auto pilot because I know the material so well and I have planned around obvious blocking sounds. I do a bit of breathing before hand to stay calm and tell myself I am awesome and this is just a bit of talking and will only take 20 minutes. I don't beat myself up afterwards if it goes poorly, it is what it is. Tick it off and move on.