When you exit your plane you will have to go through immigration, but before you reach the immigration many tour company stands will be setup and they will be asking everyone who they purchased there vacation through. If you did buy you vacation at one of these companies make sure that they do not over charge you for your visa stamp. The stamp is clearly marked $25 do not pay anymore.
Tip: You can simply walk around the tour company stands and buy your stamp from the airport immigration.