Do wear red, white, and blue. These colors look great together and just happen to be USA's flag colors.
Don't wear an an American flag shirt unless you're an elementary school teacher. Opt for more subtle patriotism.
Do go for the pinup look - short red shorts/skirt and a blue-and-white striped sailor T or tank. Pair the look with pearl earrings and a flirty ponytail.
Don't forget your sunblock. Red should should be the color you wear, not are.
Don't get stripy with the self-tanner. I recommend L'Oreal Sublime Bronze Self-Tanning Gelee for a non-streak look.
Do bring a pair of flip-flops and a pair of fashionable shoes. That way you can chase the parade candy during the day and look all sorts of sexy at night.
Don't wear white bottoms. On a holiday where candy is strewn about and the grills are a-cooking, there's bound to be some gum/tootsie roll/spilled drink that you'll inevitably sit on.
Do have an extra pair of sunglasses on hand. Someone wearing white shorts will probably sit on your first pair.
Do take a moment to contemplate the awesome country that you live in which gives you the freedom to choose what you wear.
And I'm not forgetting about all of you international peeps. If you're not in the States, you can still have fun celebrating a Fashionable Fourth, by wearing your favorite patriotic American designer like Ralph Lauren, Tommy Hilfiger, or Calvin Klein. Or just wear something from the Gap. I won't judge. Okay, maybe I'll judge a little. Wear something fashionable from the Gap.