[ramchip]

"Turn right at the next crossing, then at the 4th street turn left, then after you see the Buddhist temple turn right". Major streets also have a name, and there are maps at a lot of places, most importantly at the train station. Around my place there are even detailed, apparently hand-drawn maps with the shops' names written on them.

In the block themselves there may also be a map of the block with the houses and the family names of the owners. Houses themselves don't have a number plaque but they have the owner's name at the entrance. Apartment buildings tend to have a (more or less pompous) name as well. Here "mansion" means an apartment :)

Generally you don't need to ask though, since the websites for japanese shops usually have a detailed map, and people who invite you will give you landmarks.