Step 1: The Cuts
First, cut off the bottom hem...
and cut about two inches off each sleeve.
Then cut out a wider "boat neck".
Step 2: The Darts
Turn the shirt inside out, and mark four equal triangles.
Pinch the fabric according to your markings and pin.
Step 3: Sew It Up
After pinning all four darts, sew along the drawn lines.
You've just created closed darts!
Step 4: Open Darts
For open darts, cut out a triangle shape and sew it closed.