The most formal attire for a wedding is white tie and if you receive a wedding invitation in the mail that says white tie is required, you're pretty restricted as to what you should and should not wear. According to the guru of etiquette Emily Post men should wear a tailcoat, a formal white shirt, white vest and tie, white or gray gloves, and black opera pumps (shoes without laces). For female guests, a formal floor-length evening gown is the right choice.

A black tuxedo or evening jacket and matching trousers are standard for men at a black-tie event, but leave the white tie at home. Gentlemen should wear a black tie, black vest or cummerbund, and suspenders. During the summer, a white dinner jacket and black tuxedo trousers are also acceptable according to Emily Post. (Other experts will accept a conservative black suit as a substitute for the tux.)

For the women, there are two options. You can go a bit dressier and wear a formal floor length gown, or choose a short, dressy cocktail dress.

For a black tie optional event, guests can always wear the same attire as for a black tie event. For guests who want to go a bit more casual, gentleman can wear a dark suit with a white shirt and conservative tie. (Note: Not every etiquette expert thinks the "optional" phraseology is necessary, but it does serve to emphasize that a tux is not required.) Women can feel free to wear dressy separates if they choose.

This is something you may not see very often, however, there are some weddings that ask guests to wear "creative black tie" attire. A tuxedo is traditional for men, however, you can have a little fun with this particular tuxedo by wearing a colorful tie, cummerbund, and shirt. For the women, anything goes, from a floor length gown to a short, dressy cocktail dress, but accessories like boas, a colorful shawl and/or jewelry are encouraged to dress things up a bit.

For a semiformal wedding, a dark suit with a white shirt and conservative tie is suitable for men. For the ladies, a cocktail dress or a long, dressy skirt with a top are suitable. If the invitation does not make note of a specific attire, these are the guidelines guests should follow, but try to help guests by being as specific as you can on the invitation or on your wedding website.

A casual wedding held outdoors or on the beach is much more laid-back, especially when it comes to attire. Male guests can't go wrong with a nice button-down shirt with tie and khaki pants, a sport jacket or sweater can also be worn. But according to Emily Post you may also be able to get away with khaki shorts or Bermudas and a polo shirt. For the ladies, a sundress is perfectly appropriate for any outdoor or casual wedding, just be mindful of the fabric. You don't want anything that looks too formal. To see a full attire guide for other types of events visit emilypost.com

The MOB and MOG dress-buying rule is simple: The MOB chooses her dress first, then lets the MOG know what she's wearing. Of course if the two women are friends, they can go shopping together with their color palette in mind (that should be determined in a conversation with the bride), or they can speak by phone about their plans. The goal isn't to match perfectly, but rather not to clash. For example, if the MOB wears a long eggplant-hued dress, the MOB should wear an equally rich color, like jade or bronze. One more thing to remember: The dress code of the wedding -- and the length of the bridesmaids dresses -- should determine the length of the MOB and MOG's dresses.

The dads' dress should exemplify the formality of the event -- think of them as the sartorial leaders. If the event is black tie, they should wear tuxes; if it's cocktail attire, they should wear black suits. If you'd like them to match the bridal party (neither of them is technically a member of the party, however) you can ask them to match their ties to the color of the bridesmaids' dresses or request that they rent tuxes with the groomsmen.

Etiquette books say yes, believe it or not. But our stand is a little bit different. Okay, a lot: We say no. If you do show up in white, you're not technically doing anything wrong, but people might talk (almost everyone who hasn't read those etiquette books thinks this is wrong) and you'll be known as "the girl who wore white at so-and-so's wedding." It's just not worth it. Let the big day be about the guest of honor -- the bride -- and save your white dress for a special occasion that doesn't involve vows.