Forbes published a list of "Ten Guaranteed Ways To Appear Smarter Than You Are" including wearing glasses and using graphs in your presentations.
My favorite one actually comes from The Bible. Proverbs 17:28 (NLT) says "Even fools are thought wise when they keep silent; with their mouths shut, they seem intelligent." In other words, if you don't have anything smart to say, don't say anything at all! ~Murphy