Before entering
بِسْمِ اللَّهِ
In the Name of Allah.
Bismillaahi
Then
اللَّهُمَّ إِنِّي أَعُوذُ بِكَ مِنَ الْخُبْثِ وَالْخَبَائِثِ
O Allah, I seek protection in You from the male and female unclean spirits.
Allaahumma 'innee 'a'oothu bika minal-khubthi walkhabaa'ith.
Al-Bukhari 1/45, Muslim 1/283. The addition of Bismillah at its beginning was reported by Said bin Mansur. See Fathul-Bari 1/244