There are a few ways to protect yourself:
—Wear special viewing glasses such as solar eclipse glasses. You can buy them online or at your local museum. Alternatively, you can go to a hardware store and get a pair of welder's glasses, but make sure it's number 14 or darker. Or make a pinhole projector with cardboard. Do not watch the transit with regular sunglasses.
—Peer through telescopes outfitted with special filters at viewing parties hosted by museums, observatories and astronomy clubs. Many will also have experts on hand who could talk about the history and significance of a Venus transit.
—Tune in online. NASA, Slooh.com and the Exploratorium in San Francisco are among those that plan live webcasts.