A flaming person is one that becomes fascinated with religion, sports, school, etc...and is very vocal about it. Sharing new facts and ideas with anyone who is willing to listen. Constantly referencing different things.
She was a flaming Christian. She would quote from the bible on the regular and say "Praise the Lord."
A person you know is gay without ever speaking to them. Someone who, after you pass them on the street, you turn to the person you are walking with and say, "Man, that guy was gay."
"Did you see that stylish looking guy singing 'If I Could Turn Back Time'? He was flaming!