If you are an avid thrifter, don't be sad when you find a shirt fits but is not tailored! Take it in using this simple tutorial.
Thread to match project
You need to use the buddy system for this project unless you magically have a dress form of yourself. So make a day of it and partner up! Take the time and line up your side seams if you are taking darts out of the side. This may take a few tries, but once you get the hang of this it's easy.