first i took in the sides so it would actually fit, and hemmed a few inches up. then i cut the sleeves off the shirt, then across right under the collar and lowered the back. then i made the sleeve for the drawstring by folding an inch over, pinning, and sewing. i used a pink strip of fabric from one of my other shirts as the drawstring, and voila! i don't know if it's technically a halter top since the drawstring comes out in the middle, but it's close enough. enjoy!