Here are nine science-backed tactics to help you do just that. Even if you'd never use them, they're good to know--in case someone else is trying to use them on you.
1. Keep your eyes open (literally).
Writing in the Journal of Experimental Psychology, researchers said they found people whose eyes drooped were perceived as being less intelligent. Their theory is that drooping eyes suggested depression or fatigue, both of which "adversely affect cognitive capacity."
2. Lose weight.
"A Czech study found that certain facial features--narrow faces, long noses, and thin chins--correlated with both perceived intelligence and attractiveness," reports The Atlantic. Barring plastic surgery, that means losing weight.
3. Be perceived as a teetotaler.
Researchers at the universities of Pennsylvania and Michigan came up with this research, which they termed "the imbibing idiot bias." In short, they found that simply holding an alcoholic beverage leads people to be "perceived ... [as] ... less intelligent than those who do not."
4. Wear thick glasses.
"Wearing eyeglasses can lead strangers to regard you as more intelligent," reports The Wall Street Journal, citing a 2011 study in the Swiss Journal of Psychology. However, the effect is most pronounced with thick glasses; wire rim or rimless glasses didn't carry the same benefit.
5. Wear a subtle smile.
Similar to the findings on keeping your eyes open, the same study found that "mouth curvature"--basically a subtle smile--suggested increased intelligence.
"People over generalise in judging those with droopy eyelids and a frown as being tired and having a low mood, both of which have a well-documented detrimental effect on cognitive performance," the study's lead author told the Independent newspaper.
6. Never swear.
Harris Interactive surveyed 5,800 hiring managers and workers about their attitudes toward people who swear. Result: 54 percent said they thought swearing made people seem less intelligent. Larger percentages said it also made them seem less professional, and called into question their control and maturity.
7. Make eye contact and look directly at people.
Nora A. Murphy, an associate professor of psychology at Loyola Marymount University in Los Angeles, has done extensive research in this area, which suggests that "one of the strongest and most accurate signs of intelligence is looking at others when you are speaking to them," she told The Wall Street Journal. "And put away that phone."
8. Use a middle initial.
This one is straightforward. Writing in the European Journal of Social Psychology, British researchers said they found that "the display of middle initials increases positive evaluations of people's intellectual capacities and achievements."
9. Speak clearly and pleasantly.
Some people try to use big words or confusing manners of speech to make themselves seem more intelligent. It turns out that's exactly the wrong thing to do. Instead, be as clear as possible in your communication.
The research behind this claim comes from the journal Applied Cognitive Psychology, and its authors must have a sense of irony. The title they came up with for their article?
"Consequences of Erudite Vernacular Utilized Irrespective of Necessity: Problems With Using Long Words Needlessly."