I do not believe there has ever been an official suggested order. The most common advice I have seen, which I agree with, is that chronologically may be your best bet (with some suggesting to avoid recent releases of very early work, where he had not yet found his voice). As time progressed, the combination of drug use and his growing paranoia led to his works become less about science fiction and more about philosophy. By reading chronologically, you're likely to find the work more accessible. By the time you get to Valis or The Three Stigmata of Palmer Eldritch, you will have a better chance of understanding where he is coming from and therefore finishing the stories.
The other decision to be made is whether to start with the novels or the short stories. Again, my personal opinion, but I think that the stories provide an easier entrance into his oeuvre. Ultimately, there is not much continuity between his works, so you're pretty safe starting anywhere.