Honor your mother and father - the best way to do that is to be honest about your feelings and who/what you see yourself as. Tell them that you are an atheist. Be extremely respectful of your parents (not necessarily their beliefs). Maintain your calm and assurance in your position - be confident and serene. Let your parents see a model of an atheist that destroys their preconceived ideas of what one is. You will be respectful, polite, calm, confident and above all you must show them love. DO NOT criticize their beliefs (It'll make things rough on your living situation). I bid you safe and light passage through this place in life.
One side note...
Go to church from time to time (unless it just completely SUCKS!). This may ease the sting to your folks (they may secretly pray that you'll come to Jesus, but this keeps them mindful of what matters - your best interests, albeit in a nonsensical fashion). Also, whenever I attend a church (a rare occasion) I use the opportunity to interject some truth into the conversations I inevitably end up having while attending the gatherings. I love indirectly challenging certain beliefs and leaving the people scratching their heads - my having just undone the pastor's self-serving message. Yes, church can be a great place to share the truth with people who desperately need to hear it and see it lived-out. Good luck.
One side note...
Go to church from time to time (unless it just completely SUCKS!). This may ease the sting to your folks (they may secretly pray that you'll come to Jesus, but this keeps them mindful of what matters - your best interests, albeit in a nonsensical fashion). Also, whenever I attend a church (a rare occasion) I use the opportunity to interject some truth into the conversations I inevitably end up having while attending the gatherings. I love indirectly challenging certain beliefs and leaving the people scratching their heads - my having just undone the pastor's self-serving message. Yes, church can be a great place to share the truth with people who desperately need to hear it and see it lived-out. Good luck.