A deluded person is more likely than not one who...
1) Was born and raised into his or her religious faith. Just taking the odds at face value this is non-controversial and undeniable given the number of religions propagated around the globe and adhered to with utter and complete confidence as the one true faith.
2) As an adult never adopts nor cultivates the adult attitude of doubt. All adults must revisit the religious faith taught to them by their parents, since #1 above is undeniably true. That means they must doubt. Doubt is the adult attitude.
3) Never reads widely or is exposed to other points of view in the media. I'm talking about non-fiction works about the sciences, different cultures, different faiths, and those written by skeptics or non-believers. To escape from being deluded believers should read books that are written by people within different cultures and faith communities, and watch programs on the History Channel, National Geographic Channel, Discovery Channel, PBS, 60 Minutes, Dateline, and yes, YouTube.
4) Does not travel widely including travel into different cultures. A deluded person only experiences a small slice of the pie. One must experience the world to see how others live. The more the better.
5) Stays within the social confines of like-minded religious people. The Amish are the extreme examples of this. Many believers only have believing friends. Even if believers cannot travel the world they can still step outside their social grouping to meet other people who think differently. Most believers do not trust people of different faiths or non-believers. Seek them out. Attend a freethinker's group meeting. Get to know them. Become friends with them.
6) Never studies deeply into the nature of his or her adopted faith. The more you know the less you believe, the less confident you become, the more you doubt.
7) Preaches to people who think differently rather than rationally engaging them. I am constantly amazed, bewildered, frustrated, and bored with the kind of responses I see from believers who comment here at DC. They come here preaching. They pontificate. They quote mine from the Bible. They even say we're going to hell with glee. Many of them merely mouth the words of the creeds and affirm what they believe rather than actually engaging us with a rational discussion about the basis for believing in the first place. They come here preaching to us from an ancient superstitious set of texts we don't believe rather than showing us why we should believe it.
8) Claims he or she does not need evidence to believe. Take notice Alvin Plantinga and Bill Craig! This is utterly delusional thinking especially when we consider all of the things they must take as properly basic beliefs coming from the witness of the Holy Spirit. Anyone who claims their faith does not need evidence, even if true, ought to take a reality check.
9) Must be convinced that his or her faith is impossible before seeing it as improbable. Time after time believers will claim I have not proved that their faith is impossible, and so lacking this kind of proof they still claim to have a reason to believe. However, we're always talking about probabilities, so even if it's still possible to believe in light of a number of problems for faith it's still an improbable faith.
10) Must denigrate the sciences in order to have faith. This is what I see time after time. Believers denigrate the sciences is a number of ways in order to believe. That's because faith demands it. Some believers don't even know what I'm talking about. That's what I think. Since science tells us prayer doesn't work then it doesn't work. It tells us the universe is 13.7 billion years old. It tells us we evolved. It tells us there was no Israelite Exodus from Egypt. It tells us the Nativity stories in the Gospels could not be true. It tells us virgins do not have babies. It tells us that dead people do not bodily rise from the grave. Christians must denigrate science in order to believe. Science or Faith? Science has a track record. Faith flies planes into buildings. Science all the way, hands down. End of story.