Stand during the fitting process and walk a few steps to make sure the shoes are comfortable. They should not hurt or be too loose. Do not expect shoes to stretch. Your heel should fit snugly in the shoe with no slippage. When the shoe is on your foot, you should be able to freely wiggle all of your toes.
Sizes vary among shoe brands and styles.
Judge a shoe by how it fits on your foot not by the marked size. Try on new shoes at the end of the day. Your feet normally swell and become larger after standing or sitting during the day. Toddlers do not need shoes in a protected environment such as a home. When buying shoes for your toddler to use outdoors, avoid shoes with heavy or rubbery soles that stick to a surface and cause falls.