How do you know if there's a need to remove your slippers?

[Mashiiro]

One of the best indication if there's a need to remove your slippers is the sudden elevation of the floor in a home. House entrance are usually raised about six inches indicating that you need to remove your shoes or slippers. On the other hand, if its a tatami mat floor, the elevation is around one to two inches. If you're in doubt though, the best plan of action is just to remove there, being extra polite wont harm anyone.

[Tara4Eva]

Going inside a house is the most obvious one.

[FoodieSam]

I've seen characters changing their footwear when they enter a house in anime. You take off your shoes in the entrance area, then wear slippers, especially if you're a guest. They usually look plain white on the anime I've seen, and I've always wondered if anyone ever has ones with colourful designs or patterns on.
If the tatami is elevated, do you take the slippers off again when you go on tatami mats? Why's that?
Aren't there special bathroom slippers as well? I read some funny stories about people who forgot to take them off, then they got some really weird looks from Japanese people. I guess it's like leaving the bathroom with a piece of toilet paper stuck to your shoe.

[Mashiiro]

Tara4Eva That's a way to be literal! :P
FoodieSam Yes. They do have special bathroom slippers, I think that's because they don't want the house slippers to get wet since it would cause more hassle in cleaning those. I think you need to be bare footed in tatami mats? I'm not sure, anyone who knew /familiar about this, please enlighten us.

[Yagami]

I guess it's like leaving the bathroom with a piece of toilet paper stuck to your shoe.

Nyaha! You're right about that. It's a norm for them to remove your shoes when entering a house or a traditional Japanese establishment. And if you think about it, we use our shoes outside the house and it gathers all the germs everywhere we go. Then once we get home, we still use it on our own floors? It may sound convenient but it's outright dirty. That's just how they see it I guess. And it's really part of their culture to always be clean about everything that's why they even have lots of public baths available in every city.