Funnily enough I have just returned from a Stag do in Bratislava... I'm no fan of Slovakia, but the beer and food was cheap, the weather was good and there was plenty of guns and strippers to keep the Stag happy... I never want to be a best man, and I never want to have a Stag do :-)
You will be required to get the stag to the wedding on time and give an amusing speech, other duties will be assigned to you as per the wishes of the Stag.