If you want to look like you just attended the Woodstock Festival or a regular in the Haight-Ashbury district of San Francisco in the Summer of Love, fringe everything, don a peace sign and, as Scott McKenzie sang in the 1967 hit "San Francisco (Be Sure to Wear Flowers in Your Hair)," "be sure to wear some flowers in your hair."
Show some skin. Many hippies at the Woodstock Festival went totally nude. If you're going out in public, at least wear some pants. You can go shirtless and wear a vest over your bare chest.
Go peace-sign crazy. Wear peace-sign T-shirts, necklaces, buttons, bracelets, rings and anything else you can get the peace symbol on. While you're at it, flash the peace sign as often as possible.
Go wild with your hair. As Five Man Electric Band put it: "And the sign said long-haired freaky people need not apply." Grow your hair out as long as possible. Don't wash it very often and put it into dreadlocks. You can also adorn your hair with bandanas and headbands. Or just find a long-haired wig.
Wear sandals. If you're not in a store or around an sharp objects, go barefoot. Its even more authentic.
Wear tie-dyed clothing, whether it be a T-shirt, headband, vest or all of the above.
Dress in vintage clothing. Clothing can be as old and grungy as you want it. Old military jackets are popular, as worn by John Lennon during the anti-war movement. If it's fringed, even better.