Unlike in Catholicism, there is no head of the Jewish religion. There are chief rabbis of various countries, but they function more as spokespersons on behalf of the Jewish community, rather than as final legal authorities for the Jewish community (though sometimes they are final authorities for micro-communities).
When looking for advice on how to practice Judaism, or how to act in a certain situation, ultra-orthodox Jews consult rabbinic authorities of their specific community. Modern orthodox Jews go to rabbis of their communities who in turn usually refer to the writings of one of four major orthodox rabbis “of the generation.”
Conservative and Reform rabbis have rabbinic committees on Jewish practice that make decisions on policies within that particular movement or branch of Judaism. In most cases, Reform Jews take these policies under advisement when making personal decisions. Conservative Jews are more likely to take the policies as decisive, but many just take them as advice only.