Dua - When leaving the house
بِسْمِ اللَّهِ تَوَكَّلْتُ عَلَى اللَّهِ وَلَا حَوْلَ وَلَا قُوَّةَ إِلَّا بِاللَّهِ
"I depart with Allah's name, relying on Him. It is Allah who saves us from sins with His guidance (the ability to do so)." (Tirmidhi)
It is stated in the hadith that if a person recites the above dua and departs then there is an (unseen) procalamation that his need will be fullfilled and that he will be protected from any harm or injury. On hearing this dua, the Satan goes away from the place and refrains from troubling the reciting person.
Also look towards the sky and recite:
اللَّهُمَّ إِنِّي أَعُوذُ بِكَ أَنْ أَضِلَّ أَوْ أُضَّلَّ أَوْ أَظْلِمَ أَوْ أُظْلَمَ أَوْ أَجْهَلَ أَوْ يُجْهَلَ عَلَىَّ
"O Allah, I seek refuge in You from misleading or being misled or oppressing or being oppressed or from being ignorant or bearing the result of ignorance".