Oftentimes, persons are presented with invitations that have no dress code specified and for some reason you are unable to contact the host to find out what exactly should be worn. There are a few things however, that can be used to indicate what is expected of you in the dress department when you show up at the event.
The time of day can help you to determine what exactly should be worn to an event that sometimes doesn't indicate a dress code. Events held in the evening hours are more formal, whereas events held in the morning hours tend to be more casual. There are likely to be candles lit at an evening event, which calls for more dressy attire. A mid-morning brunch, on the other hand, is more likely to be outdoors in the sunlight. For women a snazzy black dress would be ideal for an evening event, and a sheer high-low dress would be ideal for a morning event. For men, slacks and a button-up shirt would be fine either time, with perhaps a blazer being thrown over the shirt in the evening.
Events held in a formal location require more elegant attire, whereas events held in a more casual location call for a more relaxed attire. For instance, casual attire for a backyard fete could simply mean a cotton dress for women or trousers and a button-up shirt for men rather than shorts or pants. However, an event held in The Jamaica Pegasus ballroom serving champagne probably requires a pantsuit for men and a floor-length gown for women.
The type of event you are attending is another key factor. A ball that is mandated as formal refers to a floor-length dress for women, but not necessarily a full-skirted ball gown. For men, a dressy black suit, but not necessarily a tuxedo would suffice. However, lunch at a nice restaurant would probably just include jeans, shorts and other super-casual attire.
The style of the invitation is one of the best indicators to the nature of the event. If the invitation comes in two envelopes and has raised, embossed lettering on heavy, high-quality paper, then chances are you should stay more to the elegant side. Invitations such as these generally require you to get all dressed up. However, simple invitations printed at home on computer paper indicate a more lenient host. Slacks or a simple dress will be fine, just no shorts, jeans, flip-flops or sleeveless attire.
Fabric can often be the determinant for whether an outfit is casual or dressy. Silk, charmeuse and chiffon are safer bets for informal events rather than cotton, rayon and linen fabrics. Informal/cocktail dictates more flare than business dressy without being as laid-back as casual or as extravagant as formal.
Sometimes simple accessories such as fine jewellery, heels and bolder make-up meet a more classy dress code for women, indicating a higher quality event. Cufflinks and ties can often pass as an informal code for men. Accessories such as these, added to a simple pair of slacks and a button-up shirt, often perform fine for both men.