I look for 100% cotton men's shirts, and check the armpits for stains. I'm not concerned at all if the cuffs or collars are a bit frayed as I don't use them, but I do look at elbows on long sleeved ones. I shop for color. If the shirt I like is XXL, that's a bonus, but even a men's small yields quite a bit of fabric. Although thrift shops also have cotton woman's blouses, often in lovely colors, I've found that working around the darts is too much effort. Another good thing to look at is scrubs. Many of them are 100% cotton and no darts! Purchases come in the door and go directly into the washer on hot. This takes care of fading, shrinking and sanitizes it a bit. A couple years ago I went nuts and bought LOTS. I cut them all into 5" charms, reserving the yoke for longer strips as needed. I've made several quilts, gifted charm packs, and I still have lots left.