First off, in your search, think gown over dress.  Why? Gowns are long and lean styles. Always keep in mind those gowns that make you linger and look a little longer than the rest—the ones that really grip your attention.  Do you love that empire waist because the model in the editorial looks great in it?  Or do you go for the higher waistline because you instinctively know it would look great on you?  My best advice here is this: learn to accept and cherish the body you have then train your eye and thinking to embrace styles that compliment your particular assets.  Pass up any looks you could wear if only you were taller, bustier, lost twenty pounds, had wider shoulders, etc.?  Target your flaws then minimize or camouflage them; always, always heighten your assets.

* a gown with a panel or seam(s) running up the front.  The unbroken lines give you height.
*Empire waists are one of your best options considering you go floor length.  You want to keep that vertical line going.
* A V or U-neck, it gives the impression of a longer neck.
*A mermaid.  If you’re slim and petite consider this style.  It’s fitted like an evening gown up top and has all the bounce and swirl of a ball gown below.
*An A-line.  Think of it as your very own scaled down version of a ball gown.
*Sheath and evening gown silhouettes, long and columnar; they will flatter you.
* length over volume in your skirt
*Sleeves that are long and straight.
* Best proportion is a floor length gown with veil or train of the same length.
*prints and laces as well as any motifs should be scaled down and worn on the upper portions of the body.  Busy designs below the waist  (even small ones) draw all eyes downward.
*Soft and sheer fabrics like crepe and chiffon that drape to the body.
*any ball gown.  The volume in the skirts will consume you.
*heavy, elaborate fabrics like brocade or any print or design that is large.
*Wide belts, sashes and cummerbunds interrupt the vertical lines you want to create.  If you do wear a sash or belt go thin (1-1 ½ inches) and as close to the shade of your gown as you can get.
*any design with big puffy sleeves or shoulder pads.
*Any train longer than a sweep. 
 Header Photo: A modified mermaid style with a silk gauze front sash that ties under the bust line draws the eye upward. (photo by Sweet Light StudiosPhoto 2: Another empire style in lightweight fabrics, elongates. The lightweight fabrics help reduce bulk. (photo: Carlene ImageryPhoto 3: A chemise in lightweight silks and scaled down laces also has a wide open neckline to draw the eye up.  Photo 4: An A-line in  small patterned lace organza.  Think of this A-line dress as a scaled down ball gown, giving modified volume.  Photos 5 and 6: Sheath and evening gown silhouettes--long and columar. (photos: Scott Williams Photography//Vetter Photography