Das Mädchen is actually easy as it is a diminuitive which are always neutral (granted, no one uses the root word anymore so that may be hard to identify in this case).
Outside of rare cases like that there are no actual rules, only things that can help guess, and anyone saying otherwise is simply wrong.
I guess houses build themselves for free now
And just building government sponsored free housing for everyone is great and all until you think about the fact that different people have different requirements and if you remove the landlord scalping from the picture it doesn't actually save any money since it'd just be paid for by taxes.