At home, take them off at the entrance
At home, you basically take off your shoes at the entrance (genkan). A shoe cabinet, shoes lined up, or a floor that's raised a step higher may all be signs that you should take off your shoes.
Places where you use slippers
There are also places where you use slippers after taking off your shoes. However, people sometimes take off their slippers before stepping onto tatami.
If you're not sure, ask
You can often tell just by looking at the entrance. If you're not sure, it's fine to ask.
Japanese you can use today
"Do I need to take off my shoes?"
