The sizing for each item is approximate. If you would like a more exact size here is where the measurements should be taken:
Hats: Measure the circumference and also from the crown of the head to the middle of the ear.
Booties: From Heel to big toe, measure both feet and pick the larger of the two.
Sweaters and dresses: Measure the chest, from bottom of neck to desired length, shoulder to wrist, waist.
All my items are made using a machine washable yarn. However, for longer use handwash using a mild detergent reshape and air dry.