Shrine related

As a foreigner is it appropriate to assist in helping cleaning a shrine? I would like to do some good deeds while I visit.

A local Japanese will know more - but it's not normally completed by visitors. It might be possible to meet a group of people who work at a shrine and help with general upkeep - but I have no idea how this is done....

When you say "assist in helping cleaning a shrine," you're talking about participating in some sort of event where the shrine has asked people to help them clean it, right? In that case, you shouldn't have any problems as a foreigner. Shinto doesn't really have an equivalent to, say, Christian baptism, in which a person affirms their faith as Shinto, so it's unlikely that anyone would take offense at a foreigner taking part in such an event because they're "outside the faith."

Ultimately, whether or not it's OK for you to participate is going to be up to the shrine. If they say it's OK, you're unlikely to have anyone picking a fight with you or them over it. However, it's possible that a shrine would not allow you to participate if you don't speak Japanese, and therefore wouldn't be able to understand instructions about what needs to be done and how.

On the other hand, if you're asking about whether or not it would be appropriate to just on your own start cleaning up a shrine you come across, then yeah, most people would think that's kind of weird for a person to do, regardless of whether they're a foreigner or Japanese.

Yes you can if you have permission from the owners.

Ask them first. Don't just turn up and start touching things.

That's nice of you, wanting to do good deeds to help out while you visit Japan.

A simplier way would be to pick up random litter that you spot while walking around in Japan, yes there can be quite a bit if you're in the right area. The issue would be how to dispose of it afterwards as bringing it back to your hotel would be rude as hell, and bringing it to a conbini even ruder still.

I would like to do some good deeds while I visit.

Does it have to be a shrine? Among the most common things one can do to do good deeds in Japan is to contact the local city hall (open only on weekdays) to see if anyone is looking for volunteers.

People may be looking for those who can clean up on behalf of residents who suffered natural disasters. Or other non-profit organizations could be looking for visitors who can share their experiences about their country. A city hall is an ideal place to collect that kind of information.

As for shrines, I think it totally depends on the shrine, and city halls are supposed to have nothing to do with religious organizations. What you could do is to visit one of the smaller local shrines (something we in Japan call a Hachiman-jinja 八幡神社), perhaps buy an omamori there, and while you're at it, ask the clerk to see if there is anything you could do.

The following are handy phrases:

Jinja no tame ni nanika shitai desu. (I want to do something for a shinto shrine.)
O-souji shitemo iidesuka? (May I clean up for you?)

Remember that you're expected to bring your own tools, or else you'd be borrowing someone else's brooms and cleaning cloths.

Just to add to The Friday Man's post, I've picked up random litter as a Japanese traveler within Japan.

While traveling to a small island, I was met with bad weather and had nothing to do. So I asked the hostel I'm staying to see if I could do a "beach clean". The beautiful beach in front of the hostel was quite dirty by the litter that had been blown from the sea while a previous storm. The hostel was nice enough to give me a big litter bag, and told me the place I could leave it.

It was worth while, because the litter suggested local life that would be difficult to study on my own, such as tiny fisherman tools and old-fashioned face cream, as well as some food packages with foreign prints on them.

The hostel also told me that I was only the second person who ever did a beach clean, and since I did it so thoroughly, they offered me a free drink in the evening. Of course, I requested one of their highly recommended shochu ;)