Start With the Shoulders

The shoulders are the single most important fit point, and the hardest part to fix later. The shoulder seam should land exactly where your shoulder drops off into your arm.

After the shoulders, check the chest and torso. Pinch the fabric at your side: about one inch is the sweet spot. Much more than that and the shirt is swimming on you. If the fabric pulls into little X-shaped wrinkles across the chest when you button it, it is too tight. One inch means the shirt skims your body instead of fighting it.