As a teacher of music, this is a common question I hear. Every child is unique and while there is no one right answer, I can offer a few guidelines.
One of the first “games” I play with my younger students is to have them order the letters of the alphabet. This is a chance for them to show off their knowledge, build confidence and break the ice with their new teacher. I do this by giving them a stack of flash cards, each with one letter on it. By connecting this to the musical alphabet, there’s usually an “a-ha” moment. So if you’re child knows their ABCs, it will be easier to connect the dots to the musical alphabet.
Having a child who is passionate about music is probably the most important thing.