I recommend introducing scissors as early as 2 years old with adult supervision, of course! Early exposure is the best way to help little ones learn good positioning.
Before introducing your little one to use scissors, ensure they do plenty of fine-motor activities that will strengthen theirs hands, finger muscles and improve bilateral coordination (to use both sides of your body at the same time). Using tweezers and scoops in their play is a good place to start!
If you notice your child's dominant hand is left- please buy them a pair of left handed scissors.
Tell your child you have to be able to see the smiley face all the time while they are cutting.