Surprisingly not a great deal.

They're nice, but you don't need a sacred place like a sacred grove, shrine, or temple.

It's good to have someone who knows the rituals, but you also don't need a theologian or priest.

Religious paraphenalia can help you focus, but alters and sacred symbols aren't required.

Religious texts and stories can expand your understanding, but holy books and formal mythologies aren't essential.

And yes, there are culturally defining practices that identify it as shintô, but there is no one practice that is indispensible — old practices are dispensed with and new practices are incorporated all the time.

So what is needed?

Just two things; the first thing is that you be one of the "folk" — that is that you are a member of a community. Just that — your social standing, your occupation, and your status within that community aren't important; only your belonging is.

And the other needed thing is a sense of the sublime and a willigness to acknowledge it; an ability to recognize that something "out there" moves you to feel awe, reverence, gratitude, or even terror.

That's all there is to it... and it pretty much applies to most expressions of folk religion.