Short tops and shorts should be left at home. 3/4 or longer tops or blouses and long trousers are recommended. Note that as a woman, you should take a headscarf or something similar with you to cover your hair and shoulders. Men should wear long pants and bring t-shirts.
In Iran, it is not customary to touch someone of the opposite sex, to shake hands in greeting and parting, or to shake hands with a girl to help her. When communicating, men usually turn to men and women to women.
In Iran, homosexual acts are a criminal offense and in some cases are even punishable by the death penalty. We therefore advise you to be careful.