I'm going to church. I'm going to the Church of Saint Andrews. I'm going to a mosque.

You'd say going to church but going to the mosque. I hope this helps.

You do not go to THE home or THE school or THE church. You go home, to school, to church. If you are distinguishing one church from another, say the small church or the church on Main Street.

You say “I go to church” when you wanna highlight the fact that you practice... you say “I go to the church” when you are indicating that you’re going to the church you belong to or you frequently go. I believe the same goes for mosque.

I say both. I say, I'm going to church when I'm thinking of church services, an activity. I say, I'm going to the church, when I am thinking of the building itself. But there is no rule differentiating the two.