The only way to know the spirit intended thereof, to be able to answer the questions knowledgeably and correctly, and to know what to do in most situations, is study. Sure, you can rely on a rabbi or some other religious figure for advice (and that especially makes sense for the really complex questions). But, it's ultimately up to you to decide if the given answer truly fits in with the teachings of the Torah.
Lest someone think I am speaking of, say, Reform Judaism versus traditional beliefs, I believe that one needs to follow the Torah and the Oral Torah as given. And to learn the true meaning of these things requires study with a traditional rabbi, not someone from one of the offshoot denominations. I'm merely suggesting that you shouldn't rely completely on what someone else tells you about it. (In particular, you should pay no attention to what I say on the subject! I'm perenially confused, and maybe should not have written all that.)
And there's a lot more than halakah (Torah law) to being religious. Spirituality plays an essential part, and study is of great assistance here as well: study of the Torah, and of other related materials.
