*Define The Waist:
Wether for you this means tucking in your top, adding a belt, or both, be sure that your natural waist isn't buried under a sack of fabric. Wearing a more fitted top to contrast the looseness of the skirt is another good way to emphasize your silhouette, and show off the slimmest part of your body.
Show off:
You've already covered up about 60% of your body with a single article of clothing, maybe try showing off some of the other 40% a little bit. Go for a plunging v-neck, fitted blazer, a sheer breezy with a bra, a crop-top, or maybe even just a sexy little tulip back tank top.
*If your maxi skirt / dress is sheer, try wearing it with a mini slip or perhaps no slip at all. You can use your legs to add the edge and sexiness to your outfit, and cover up your top half a bit more.