The answer might be funny or even shocking to you. 

1st prepare, 2nd rehearse in front of a mirror and record yourself with your mobile phone ( if your cloud), Practice makes perfect ( Q card helps ). You can use Google Hangout and practice that with a friend ( hangout video conferencing can handle up to 10 people )... Now the shocker -  As you stand in front of the public scan them from left to right, close your eyes and imagine, they are all wearing only their underwear. Then naturally,  you smile and then start. Use your hand and body to transfer the presentation energy to audience  ........For some reason, this works.