Believe and not believe, because some of them is win and some are not. Usually in my country people look for number to lottery in graveyard or maybe go to shaman. But one thing that always on my mind is, if the shaman really can guess the number, why he not buy it for himself to be rich. 
Haha, I know about this and sometimes it's funny to know! but if we laugh at this in front of people who do that we can be considered fools. like you said, if a shaman knows something like that why doesn't he enrich himself? this is the basic logic about it, but the people who do it don't think about it.