A common mistake in teaching about the Trinity is to refer to the Three Divine Persons as “God,” “Jesus,” and the “Holy Spirit.”
Can you spot the problem?
More and more, western society is losing the understanding of who God is and by referring only to the Heavenly Father as God, we imply that the Son and the Holy Spirit are not also God. It may seem nit-picky, but seemingly minor distinctions like that are the root of many heresies, including Arianism which held that Christ was a creature, made by God much like we are.
Better to refer to the Three Persons as the Father, The Son, and the Holy Spirit, or much better (especially if you’re not certain the one you’re speaking with fully understands), God the Father, God the Son, and God the Holy Spirit. It’s a little cumbersome, but leaves no room for doubt.
Image Credit: Lucas Cranach, the Elder
Family Formation 
When the kids in my class say “God” for the 1st person of the Trinity, I ask them to be more specific. It trains them to avoid saying God unless they include all 3 Persons.
I think that’s a great idea – especially in a classroom setting where we want to capture every opportunity to learn!