Wedding guest looks are so fun to put together. As long as you're not wearing white and the wedding doesn't have a color theme we have a few ideas to help. First, you must know the venue, this will dictate how dressy you must be, and should also dictate your shoes.
If you're going to a cathedral/church wedding followed by a fun reception you have to keep two things in mind. One; you're going to a church so be appropriate enough and this could mean wearing a silky scarf over your shoulders for the service and then taking it off for the reception. A slip dress and heels is a great go to for pretty much any occasion, especially this one.
If you're going to a garden wedding and reception, this is easy. No coverage needed, just think about your pointy heels digging into the grass, so perhaps wear thicker heels/ wedged heels so you can be comfortable. A range of dresses listed below can worn to a garden wedding. If it is a day time wedding, a lighter color would probably be best. Although, black is always in. Pick something comfortable for the weather as well.
Rooftop weddings in any city call for a sexy look. A fitted dress with deeper colors are always perfect for the occasion. Wear your best tallest heels and you're set. The dress length is irrelevant although, be mindful of the crowd.