In a trial, the jury sometimes decides innocent or guilty in the first five minutes after hearing each lawyer’s opening remarks. The deciding factor for the jury is siding with the lawyer who seems most confident. Two important lessons come from this: juries or prospects or clients make their decisions very early in the process, so put your best stuff into the open. Secondly, learn the techniques that confident speakers use.
These techniques are relatively easy to master: strong eye contact, powerful voice, good posture, animated face, arms and body, the use of storytelling, command of material, speaking slowly. Just learn to be proficient and practice 2 or 3 of them in each rehearsal and you will be a much better presenter.