Where to start? Now that's a difficult question.
I'd like to say that one should start without any presuppositions, realizing that one could be wrong about everything, but one has to start somewhere. Without presuppositions there is no starting point. Even in purely concrete subjects like math there are postulates. To get anywhere, we do have to assume a few things: first off, that human logic at its purest form has some form of inherent correctness, and secondly that our experiences are based on some form or reality around us, even if they aren't always accurate. Once one gets somewhere with these "postulates", then the extent to which these work out confirms their truthfulness, thought I guess one should be ready to accept these being wrong.
I'd also like to point out that if a certain worldview comes without consequences for disbelief, I probably wouldn't bother looking into it much. I guess this is a utilitarian view and sort of an extended version of Pascal's argument, but whatever.