When purchasing garments to recycle, I look for beautiful fabrics and unusual details. I don't have to worry about small stains or signs of wear, and size is not an issue - although, obviously a size 6 has less fabric than a size 22.
This linen blouse is a gorgeous dusty rose color and has an embroidered chiffon detail at the cuffs and hem.
When I get garments like these home, I remove price tags, then wash on a gentle cycle with liquid detergent that contains no perfumes or dyes, about 1/4 cup of baking soda, and vinegar to rinse. I am allergic to fabric softener and perfumes, so the above products are what I use for all our laundry. After years of not using fabric softener, I find it smells quite offensive. Thrift store clothing can be a multitude of perfumes and scents, so washing this way removes much of that odor. Hanging the garments on the clothesline removes any lingering odor and prevents damage from the heat of the dryer. After laundering, I begin unpicking seams, cutting off buttons and lace, etc. Formal dresses in particular have lots of fabric, often an underskirt of a different fabric, sometimes crinoline or tulle. After pressing the usable fabric, it will get cut into smaller pieces, and packaged for sale in my Etsy shop. If a fabric is really special, I'll be sure to cut off a chunk for my own CQ stash - hey, a girl's gotta have some fun!