Question: What should I wear to my friend's/relative's wedding?
First of all, don't upstage the couple. That means don't wear white, don't be tempted to go more formal than you think the couple will be, and don't dress to call excessive attention to yourself (e.g. a super short miniskirt or a sequined tie.) After that caveat, try to dress appropriately for the time of day and the setting. A Sunday afternoon wedding generally means a coat and tie (perhaps with light-colored slacks) and flowing dresses. An evening wedding calls for a suit, or coat and tie with dark slacks. Unless the invitation specifically calls for it, never wear blue jeans, even if the invite says casual. Casual in this case means your best casual, not your weekend at home casual. I have more details on what to wear to a wedding
including details on where to find clues, and specific advice for different kinds of events.