In the last three decades, the TED talk has become both a cultural phenomenon and an increasingly important credential for anyone in the world of business and entertainment.

To be invited to speak at the annual TED conference (the acronym stands for Technology, Entertainment and Design), which this year takes place in Vancouver, British Columbia, from Monday to Friday, is often the highlight of someone’s career, with the chance to be on the same stage that has served as a platform for people like Bill Gates, Sheryl Sandberg, Elizabeth Gilbert and J.­J. Abrams, and to produce a speech that may go viral and make the speaker a star.

But TED speakers face two immediate decisions when invited to give a talk: What am I going to talk about? And what am I going to wear?

The organizers understand the importance of the latter issue, and often offer help to speakers through a series of guidelines.

“Do not wear stripes, complicated patterns, bright colors that could disrupt lights or dangling jewelry,” the guidelines suggest. “Try to wear a color that contrasts with gray so that you do not blend into the background when being filmed. At the same time do not wear anything too bright.”

Sometimes the geographic location of these talks, for TED spinoffs like TEDx, can dictate what may be worn.

For a dual TEDMed conference held in Washington, D.C., and San Francisco, “casual dress is always encouraged.” In Manhattan, “dress code is comfortable – jeans, sweaters, informal is fine.” In Monterey, Calif., “dress code, as ever, is casual.”

The organizers of TEDx Macatawa, which was held in Holland, Mich., were (wisely) aware that casual ease might be taken too far: “We are interested in having you be as comfortable as possible. However, you must wear clothes.”

But as interviews with a number of speakers suggest, you are pretty much on your own when it comes to picking an outfit. Here is how a sampling of TED speakers from the last few years (from the main conference and several of its offshoots) made that decision. (More than a few seem to have ignored or been unaware of the guidelines.) These interviews have been edited and condensed for space and clarity.