The time of day, and where the wedding/reception is to be held are the keys for deciding what to wear. If I am not sure what will be the exact thing to wear, I prefer to overdress....obviously, not to the exteme of wearing a gown to a bowling alley. I would rather feel I overdid the occasion, then not show significant respect to someone's occasion, or have someone feel the 'need' to comment, "look what she wore".

I think most weddings held in the late afternoon, with an evening reception would warrant a simple calf lenght dress, in any muted tone. And, cause I don't know if you wear dressy shoes regularly or not, find a pair you will be wearing, and try to wear them a little bit every once in a while....or it will be heck on your feet for the whole day!