What should I do when I want to do something whose ruling I do not know, and whether I should do it or not?

The scholars have stipulated that it is not permissible for a mukallaf (one who is accountable under Islamic law) to perform an action until he knows Allah's ruling on it; whether it is permissible (halal) or forbidden (haram). Their evidence is Allah's Almighty saying: (O you who have believed, do not put [yourselves] before Allah and His Messenger). An exception to this is if a mukallaf is faced with an unforeseen situation (nazilah) and is in a place where he cannot find anyone to ask about its ruling, and he has not been guided to the correct answer. In this case, accountability falls away from him, and his situation becomes like that of one before the advent of revealed law, or one to whom the call (da'wah) has not reached, so he acts upon what is made easy for him.