Clarify what is expected from you; are you supposed to dress in a matching outfit with the bridesmaids, what the mother of the groom will be wearing, what theme and venue will be the wedding held at, what is the wedding color, style of the wedding.
Shop for the dress that complements your body type. For example, if you have a thicker midsection, empire waist will even out the proportions. Figure out what length you want in to be; below the knee length is ideal if you don’t like to show knees, yet still reveal some skin; midi length looks good on shorter women only when made out of light fabrics, maxi dresses elongate silhouette.