Islam is the official religion of Egypt.
Over 90% of the population are Sunni Muslims.
This percolates into all aspects of expected behaviour.
You should always dress modestly, be respectful about use of alcohol (especially during Ramadam) and be aware of prayer breaks, five times daily.
A man meeting a woman for the first time should wait for her to extend a hand.
Otherwise, same gender handshakes should be firm, ideally accompanied by eye contact and a smile.
The normal greeting is salamu ‘aleiko (‘Peace be upon you'), to which the reply is wa ‘aleikom el salam (‘And peace be upon you too').
If offered the greeting, it's rude not to reply.
The Egyptians are a very polite people and good manners are essential.
When you add to this the idea that people here dislike loosing face, you may find that people will try and oblige you, even to the point of misleading you.
(Be careful, therefore, if there is any doubt or hesitation over street directions.)
Family is at the centre of life here.
To be invited to someone's home is an honour, and you should always accept.
The right gift to bring is pastries or a cake for dessert.
Alcohol is a no-no and flowers are only likely to appreciated in Westernised homes.
Arrive a little after the set time and be prepared to wait until all the guests have turned up before the meal is served.
All the food will be put on the table in one go and you should wait to be served.
When you've had enough, leaving a little food on your plate will indicate this.
Dessert generally follows in a separate area.
Egyptians generally sit and stand closer than many Westerners are used to so try not to move away.
Same-sex conversations can be more touchy-feely than you might be used to.
If you sit alone in an empty bus or cinema the next person who comes in may well sit next to you but this doesn't mean that they want to talk to you or get to know you.