You need to practice the webinars alone but in record mode. Using GoToMeeting/GoToWebinar you can practice presenting to yourself or others in your organization. The benefit is you get used to the technical tools to prevent those technical mismanagement issues as well as practicing your pitch. ...
Practice makes perfect! If you have friends, family and/or mentors, practice for them and ask for constructive criticism. If you do it 100+ times and it's all positive feedback, there is no reason not to feel confident. I just went through @INcubes accelerator program - probably practiced my p...