Rule #1 - Never allow him to be a man of either intelligence or education.
All Christian ministers are grossly lacking in both. This is an undeniable fact. If they had either, they would never have chosen this profession.
Rule #2 - He must not exhibit a coherent or contemporary command of the English language.
His conversational English needs to denote low inteligence and/or poor education (see Rule #1), or else needs to indicate a divergent personality disorder such as megalomania. The one exception to this rule is that a Christian minister CAN be a good public speaker with effective conversational skills ONLY if he is a smooth-talking, money-grubbing scheister.
Rule #3 - He cannot be logical.
He cannot have ever had formal training in logic or philosophy or the most basic principles of debate. So when he is engaged in a disagreement with someone, he will default to shouting, bullying, or patronzing.
Rule #4 - He cannot have a character arc that involves positive personal change.
Christian ministers are not about change. They are about static, stubborn, unbudgability. So either the character must remain flat and unchanging, or he must eventually be his own undoing. The only acceptable POSITIVE character arc that a minister can go through would be if he realizes his religion is a sham and chooses by film's end to abandon his faith and profession completely.
Rule #5 - He needs to have serious sexual problems.
Religious leaders are uptight about sex. And therefore suffer from severe sexual dysfunctions, and probably also harbor many closet fetishes, possibly even criminally deviant ones. His relationship with his wife needs to be problematic on many levels because of this, and his children will also show evidence of sexual maladjustment. The overriding rule of thumb is that it's impossible for a Christian minister to be cool about sex, to have a healthy sex life with his spouse, to have a sense of humor about sex, or in any way be comfortable with it, either in himself or those around him. Be forwarned that any movie script which has a Christian minister that exhibits any form of positive sexual health will be promptly rejected and an immediate rewrite demanded.
Rule #6 - He must be intolerant of personal individuality and cultural diversity.
The Christian religion mandates that their ministers push an agenda of assimilation and ethnocentricity. They ardently strive to for cultural monopolization and homogenization. They are the religious equivalent of the Borg. All actions and dialogue of any Christian minister must exemplify their disdain for freedom of expression, and a lack of openness to alternative cultures.
Rule #7 - His tastes and overall personality must be boring, limited, and unoriginal.
CLOTHING: His profesional wardrobe should be full of dark suits. His casual wardrobe should be flannel plaid shirts and cardigan sweaters. Think "Land's End" but out of date by 15 years. His wife always only ever wears dresses, she probably sews them herself, and they will always be nauseatingly flowery prints that look like they were made from old tablecloths or bedspreads. His sons will likewise wear flannel shirts, and they will wet-comb their hair down flat and part it on the side. His daughters also wear dresses, sport long hair and no makeup, and have a hollow, frightened look in their eyes. Sleep wear for the men/sons will always be classic button-shirted pajamas with pants. The wife/daughters will sleep in long-sleeved, high-necked, cotton, white, non-romantic night gowns.
READING: He reads almost nothing but the Bible and maybe Reader's Digest. If he bothers to read fiction, it's only Christian fiction. He has never touched a classic in his life. He refuses to read news magazines like Time or Newsweek because they all support "the Liberal agenda." Maybe he reads the local town newspaper, but only to grumble and disagree with it. And since he's neither intelligent nor educated, he has no clue about Greek, Latin, or Hebrew.
HOME DECOR: Always drab and lacking in life. Furniture should be cheap knock-offs of early-American and/or colonial with plenty of finials and dark wood. If there's any artwork on the walls, it'll be just pastoral stuff or flowers. Darkened or yellowing wall-paper is perfect. If the floors are wooden, they will lack shine. Carpets are worn and uninteresting. Books anywhere in the house are rare to non-existent.
MUSIC: Of course he listens to gospel music, and maybe the classics (but he won't actually understand the classics). Secular music is of the Devil, so neither he nor his wife and children listen to it. There is probably either a piano or an organ in his house, and his wife and daughters play it. If they ever play any non-religious piano music, it's old yellowed sheet music from the 1920's.
FILM AND TELEVISION: Hollywood is a stronghold of Satan, so movie-going is forbidden. There MIGHT be a TV in the house, but only to watch the news. VCR's and DVD players are invitations to porn, so they're not allowed. And no video games either.
COMPUTERS: If he has a computer in his house, he uses it to write his sermons. He is NOT internet savvy. Neither are his wife and kids.
SPORTS: Wholesome outdoor activities are walking, fishing, and playing golf. Boys can play baseball and football. Girls can play basketball, but only if they wear skirts. All sports must be separated by gender (no co-ed sports allowed).
FOOD: Dinner is served up by his wife every night at 5:30 sharp. And it'll be some variation on meat 'n potatoes. Maybe we can allow for a pasta dish that remotely resembles Italian cuisine. But no Christian minister would ever eat Mexian, Thai, or sushi.
Rule #8 - The bulk of his time is spent writing and rehearsing sermons.
He never ministers to people on an individual, one-on-one level. Never interacts with members of his congregation outside of the obligatory round of hand shaking outside the church after a Sunday service. He never does counseling sessions. He never makes house calls. He never visits the sick. He never visits those in prison. He never meets with local community leaders--unless he's a "bad guy" minister who is covertly scheming on some political level with/against those other leaders. Aside from weddings, funerals, and the ocassional baptism (which is always an INFANT baptism) he's very self-absorbed and leads a totally insular life.
Rule #9 - His sermons are always of the "fire and brimstone" variety.
He must employ a pulpit pounding, rafter-rattling, fist-waving style of preaching, even though less than 20% of all American pastors/preachers fall into this category. And the congregation always responds with loud affirmations of "AMEN!" and "PREACH IT!" even though the vast majority of American congregations observe polite and attentive silence during a sermon. And during the worship music portion of a service, the congregation will worship in outrageous strains of Pentecostalism, including dancing, jumping, arm-waving, speaking in tongues, and getting slain in the spirit, even though less than 20% of American church-goers engage in such displays of Charismata.