In days gone by, etiquette gurus laid down elaborate schemes for calculating the formality of a wedding based on the time of day, number of guests, and length of the train on the bride's gown. These rules are somewhat like Latin, in that they're still around, but hardly anyone knows them or uses them.
So the only clue to the formality of the wedding is the fanciness of the invitation, and that is by no means entirely trustworthy, as I've seen very formal weddings with teddy-bear and Cinderella invitations. The best thing to do is to call someone involved in the wedding and ask how formal it is. For happy couples who would like to clarify the issue for their guests, here is the Practical Guide to Formality.
Close your eyes and imagine that you are surrounded by happy wedding guests. What are they wearing? If they're wearing their very best clothes -- or outfits they had to rent for the event - your wedding is formal. If they're dressed very nicely, but for some reason not in their very best (perhaps your site lacks air- conditioning, or the terrain is bad for high heels), then your wedding is semi-formal. If they're wearing clothes that won't be damaged by spilled barbecue sauce from the pig roast you plan for the reception, your wedding is informal.
The site of your wedding becomes a controlling factor here, for the excellent reason that good hosts see that their guests are comfortable. A formal garden with paths, chairs, shelter, and other amenities that make it suitable for weddings works for a formal wedding; a public park with outhouses calls for an informal event. A church wedding in a cozy church can appropriately be semi- formal or informal. And weddings on mountaintops at dawn are always properly informal, as there is no such thing as formal hiking boots.
With this decision tentatively made, your thoughts turn to the menu and entertainment. At a formal wedding, you serve food that your guests would consider appropriate for a "big date" such as a major anniversary or a romantic birthday dinner. The refresh- ments can be afternoon tea, a lavish cocktail hour, or a dessert spread, so long as they fit the guests' prevailing definition of "fancy."
At a semi-formal wedding, the menu looks more like what you'd serve at a holiday dinner or when you have good friends over to visit. At an informal wedding, you serve picnic food in a more picnic-like style. A "cake and punch" reception can, there- fore, be formal, if the cake is extremely elegant (hazelnut, perhaps, with one of those basketweave patterns) and the punch is not the red kind served in kindergarten. A full meal can be informal if it involves large quantities of finger food.
Now that the prevailing custom in the U.S. is for the groom and best man to wear tuxedos regardless of the time of day and almost regardless of the formality of the wedding (and much to the horror of conventional etiquette experts), it is difficult to lay down absolute rules for attire. Nonetheless, certain guidelines make sense.
At a formal wedding, the bride wears the fanciest dress she can stand. If her age, dignity, figure, or personality leave her less than eager to don a big white wedding gown, she can wear the most elaborate dress that she would ordinarily consider wearing to the kind of party she's holding (thus, an evening gown for a cocktail party reception, but a garden party dress for an afternoon tea). Her attendants dress comparably, with evening gowns for evening and lawn dresses for daytime. The men wear formal wear appropriate to the time of day.
At a semi-formal wedding, the bride may still wear a wedding gown, but she congratulates herself on having found one that is relatively restrained. If trains are in fashion, she may wear a short one. Her attendants are similarly a bit more restrained in their attire, and they may even wear tea-length or knee-length dresses for an afternoon wedding. The men in the wedding party wear their best suits.
At an informal wedding, the bride wears a festive and flattering outfit that is appropriate for the planned reception events. She would wear a nice suit or dressy day dress for a small ceremony followed by lunch at a good restaurant, but a cotton gown in blue gingham might be more appropriate for a hoe-down reception. Her attendants and all of the male participants similarly choose festive outfits that will not be impractical or out of place during the party.
It's important to note that the religious content -- or lack of it -- of the ceremony has little to do with the formality of the wedding. A civil ceremony (which is no longer necessarily a quickie exchange of vows) can appropriately be followed by a very elegant and formal cocktail party or dinner. On the other hand, most houses of worship (especially smaller ones) welcome ceremonies that are reverent but not too elaborately staged.
And this leads us at last to the invitations! There is a myth that the printing on the invitations should match the color of the bridesmaids' dresses -- which would render invitations difficult to read whenever the 'maids were attired in buttercup, soft pink, or stone gray.
While this "rule" is no rule at all, there's an underlying thought that isn't entirely silly. For a bride and groom who are baffled by books of invitation samples, it's not a bad rule of thumb to think about what style the bridesmaids' dresses express, then choose an invitation in a similar style. For instance, if the bride has encouraged her 'maids to choose sleek, elegant dresses, the wedding as a whole might be best expressed by sleek, elegant invitations with linear borders, angular type, and a very plain yet classy look. On the other hand, if the bride has encouraged her 'maids to choose ruffly floral dresses, the style of the wedding may be more country Victorian, and the invitations should have the same ruffly, floral look.
In general, a formal wedding calls for invitations that convey solemnity and importance to the guests. Heavy paper- stock, plainer designs, and formal wording are preferred.
A semi-formal wedding is a more appropriate occasion for invitations that feature colored designs, inspirational messages, and wording that deviates significantly from the traditional format. For a small semi-formal wedding, the bride and groom can also handwrite personal invitations to each guest.
The traditional way to handle an informal wedding was to invite guests by personal letter. A truly funky or quirky printed invitation would also work if the guest list is long (as for a large pig roast).
There are three pitfalls that it's important to avoid.