The easiest way? Go look at any free sweater pattern that matches the top you want to the dress. Divide your stitches according to the pattern, more or less, and work the same bindoffs at the armscye. (If you put a marker at the correct stitch where the underarm seam would generally be, it makes it easier to count.) You don't have to use straight needles unless you want to, you can work on your circular needles flat.
OTN: Eyelet Chemise in Handmaiden Sea Silk (colorway: Midnight). Still. And a purple Donegal Tweed set of fingerless mitts, to try out my new Hiya Hiya interchangeable needles.
Latest FO: A shrug for an Anthropologie swap in beautiful Casbah sock yarn, in Cedar, a dark green semi-solid, my own pattern. Also a quick Noro Silk Garden neckwarmer for my friend Aideen, in a vine lace pattern.
My knitting blog, Another Long Yarn