Idolatry can be subtle and pervasive. It manifests in the usual suspects like money or success and other familiar villains. But Christians ought to also be wary of the looming idolatry lurking in some of the essentials of the Christian experience.
I think of idolatry as a disproportionate worship of or devotion to something. Maybe you believe that the God who is Love—Creator and Sustainer of everything from the farthest galaxies to the nearest neurons in our brains—is the one to whom we ought to give our deepest allegiance and devotion or most permit to inform how we live and the choices we make. Idolatry, then, would be giving comparable adoration and devotion to something less worthy or worthwhile than God. Especially something that inhibits our ability to care for that for which God cares.