Avoid These Body Language Postures and Gestures When Giving a Presentation

Your gestures and how you hold yourself during a presentation convey as much as words might. Inc. has rounded up ten examples of wrong body language so you can instead look and sound professional. 

One really important piece of advice is to not speak to the screen; i.e., face the audience rather than turn your back to them. Inc. suggests a "think, turn, talk" method for presenters:

Look at an item you are discussing to gather your thoughts, turn to look at the audience, and then start speaking.

Among the article's more interesting tips is to gesture from the shoulder rather than the elbow, which looks awkward and a bit too much like you're doing the chicken dance, Inc. writes.    source