Do obey every law.
Do dress in a conservative manner, particularly when you are not in a big city, and not in a tour group.
Do take off your shoes when entering mosques or carpeted areas in private houses. Feet (especially women’s) are better being covered with socks.
Do bring a small gift if you are invited for dinner. Flowers are a good option, but expect to spend some time in a flower shop while your flowers are arranged. Sweets are another popular choice. Remember, however, that it is thought polite for someone to refuse a gift a few times before accepting. (in Persian Taarof)  It is customary to repeat every thing at least two or three times to persuade the host to accept your “yes” or “no”.
Do praise the house, the food, and the hospitality of the hosts but never praise household items, as the hosts will thus find themselves obliged to present them as a gift.
Don’t discuss politics, family relations, the role of women, and other controversial subjects unless you are in the company of close friends.
Don’t stretch out your hand to be shaken by a member of the opposite sex, and don’t ever touch any member of the opposite sex apart from close family relatives. Intimate physical contact in public is likely to cause offense. Couples can only hold hands, but must absolutely never kiss or embrace. Women and men usually kiss each other three times at meeting and parting (women kiss women, and men kiss men). Members of the opposite sex can kiss each other only if they are the closest relatives, like parents/children and brothers/sisters.
Don’t show indignation if you are physically searched by customs officials in the airports.
Don’t stick out your thumb; it is considered vulgar.
Don’t take photographs of pilgrims, religious figures, and shrines unless you receive permission first.
Don’t forget to have the name of your hotel and/or destination written down for you in Persian script (many taxi drivers do not speak or read English).
Don’t accept alcoholic drinks that may be available through the black market because that these beverages may be a health risk.