Things you need for this DIY:
✝ a long lace dress (here's mine)
✝ tape measure
✝ four straight pins
$30 for the dress
This is the easiest...
First, put the dress on and mark with pins the length you want in the front, back and on the sides. I measured 12 inches in front and back and 24 inches on the sides (up from the seam). I have to admit the sides are just a tiny bit higher than I wanted, so I advise you to make it a little longer to be on the safe side.
Make straight cuts up the sides.
To finish it up, cut along the flowers in the lace.
Feel free to wear something less revealing underneath...or more.