Questions & Answers
What you need to know before visiting Iran
I am planning to travel to Iran for a visit, and a friend of mine who is Iranian will host me. He will be arranging my visa as I am from Latvia, and I have to send him a copy of my passport.
He will follow up with the MFA to get me a reference number. I just want to know if this is the normal procedure.
In addition, I've heard many things about Iran. I want to know about Iran's code of conduct like if it's illegal for a guy to talk to a girl or shake hands in public places, about the dress code, couch-surfing, and if my mother's British nationality can cause me problems or suspicions.

Hello
First I must welcome you to Iran. You will enjoy it and you will probably come back again.
Iran a Muslim country, so dressing should be formally acceptable; there is no limitation as long as you are not naked!
It is not illegal to talk to a girl but shaking hand and touching might cause problems (It's just a probability. Just take care in the formal places like police stations. People are ok, but the police might not be!).
If you don’t have any history of getting in trouble in Iran like imprisonment or any other kind of accusations, you don’t need to worry about your mother's British nationality.
Finally, for the invitation, they need a copy of your passport and a picture so yes it is the normal procedure.