blogger wouldn't let me add any more photos on the last post, so here is post #2 with the rest of the steps! And my camera died halfway through this, so forgive the lack of photo of the final project...
Pin facing to front of shirt (facing is another piece of fabric that will end up on the inside of the garment to stablize and help keep shaping) - This facing came from another white t-shirt that was stained so I didn't mind cutting it all up:

Draw in shaping with water erasable marking pen (I wanted my shirt to have kind of a keyhole v-neck, but you could do a boat-neck, scoop-neck, true v-neck, or whatever you would like), then stitch about 1/4" to 1/2" away from edging and shaping drawing:

After stitched, clip and trip away excess fabric:

Turn facing to the inside, pin again and stitch about 1/4" away from finished edge to hold in place. I added some decorate ruffles around the edges, but it looks good plain too.