First get a plain t shirt and your favorite fitting t shirt. Next lay your plain t shirt flat and inside out. then you will lay your favorite t shirt on top of the plain shirt lining up the necklines. Trace your favorite t shirt onto your plain one. Cut off excess side material and leave space for your sleeves so you can fold them later.
First fold sleeves so they have a nice edge and sew lust the end of the sleeve all around. Then you will sew the little under arm part.
Still with your t shirt inside out sew along the sides from the bottom of the arm to the end of the shirt. Yeah!!! the sizing shall be finished!
You can draw or print out a siloette picture to use as a stencil on your shirt. (i drew a tree and stenciled it on with printer paper...don't do that lots of bleeding occurs!) So use card stock or contact paper.
lay your design out on your shirt where ever you'd like it to be and glue it down with washable glue stick...this wouldn't apply to contact paper..lol
make sure cardboard is laying between shirt and spray all around stencil and where ever you'd like. Let dry. Done!?!?!? yeah!!?!