I think you have the guts, confident with prayers are the keys to pass those question in immigration, I'm here in doha since nov. 3 2010 using business visa. I was nervous when the interview starts because I don't have much supporting documents, My brother sent me only company id and passport copy of him. I know nothing, even his exact address. I didn't passed the first interview and then I talked to the immigration supervisor that I'm going to visit my brother that worked in qatar for almost 8 years and He requested me to visit him instead of going in vacation in philippines.and asked me some things about my brother and how much show money had he passed me for the interview.