It is forbidden to read Krias Shema within four amos of a dirty alleyway or as far as the eye can see if it is in front of you. (ShA 1 – MB 2)
Dirty places are defined as having excrement and urine there. In such places, and bathrooms and bathhouses one may not even think divray kedusha. Merely speaking in Lashon Hakodesh is mutar (if not for middas chassidus). (ShA 2 – MB 9)
It is ossur to mention there one of Hashem’s unerasable names even in another language (e.g. Got) (MB 10)
You are allowed to erase Shalom even in Hebrew and Got in Yiddish because there is no kedusha in those letters. (MB 10)
A translation of one of the unerasable names is considered His name. Do not say it with no good reason. (MB 10)
To stop someone from doing an issur you should hint “Don’t do that”. If need be, you may say clearly the extent of the issur using terms of hora’ah in order to stop him. (ShA 2 – MB 14)
You are allowed to think Torah thoughts in order to cancel ossur thoughts in the bathroom. (MB 13)
It is forbidden to think about dikduk Lashon Hakodesh in the bathroom. (MB 5)
You may think about man’s lowly state, the household budget, or imagine nice looking buildings and paintings. (MB 5,6)
A person who is fluent in Torah must make the effort to remove Torah thoughts while in the bathroom. However, if he cannot manage to, it is mutar. (MB 8)
If one’s hands are really filthy he may not even think Torah thoughts. But if they are mildly dirty (e.g. he touched covered parts of his body) he may think in Torah and even say a psak din – just do not say the reasoning. (MB 15,16)