If the tag says DRY-CLEAN ONLY, follow those instructions. But, if it says DRY CLEAN it means that is is the recommended method, not the only method.
How should you decide?
Consider the fabric. Unless the label suggests otherwise, silk, acetate, velvet, wool, and taffeta items should be taken to the dry cleaner. But, cotton, linen, cashmere, polyester, acrylic, and nylon can usually be washed at home.
You should check for colorfastness before washing though. Simply moisten a cotton ball with mild detergent and dab it on a hidden seam to see if any dye comes off.
Evaluate the detailing, too. Before you wash anything with beading, sequins, stones, etc., make sure they are sewn on (you’ll see stitches, not glue) and colorfast.
Evaluate the detailing, too. Before you wash anything with beading, sequins, stones, etc., make sure they are sewn on (you’ll see stitches, not glue) and colorfast.
