When entering the toilet
When entering the toilet recite:
Bismillah "In the name of Allah"
It is in the hadith that between the eyes of Satan and the private parts of man Bismillah is a barrier therefore, this dua should be recited.
اللُّهُمَّ إِنِّي أَعُوذُ بِكَ مِنَ الْخُبْثِ وَالْخَبَائِثِ
"O Allah. I seek refuge in You from the male female evil and Jinns".

(Mishkat, Hisnul Hasin)