Prescribed means of warding off sihr (witchcraft) before it happens
Question

What are the prescribed means of warding off sihr before it happens?.
Praise be to Allah.Among the most important means of warding off the danger of sihr before it happens is seeking protection through the adhkaar (dhikr) prescribed in Islam, making du`a and reciting prayers seeking refuge that were narrated from the Prophet (peace and blessings of Allah be upon him). These include: 
1 – Reciting Aayat al-Kursiy [al-Baqarah 2:255] after every prescribed prayer, after reciting the adhkaar which are prescribed after the salaam. 
2 – Reciting Aayat al-Kursiy when going to sleep. This is the greatest aayah in the Qur’aan, in which Allah says (interpretation of the meaning): 
“Allah! Laa ilaaha illa Huwa (none has the right to be worshipped but He), Al-Hayyul-Qayyum (the Ever Living, the One Who sustains and protects all that exists). Neither slumber nor sleep overtakes Him. To Him belongs whatever is in the heavens and whatever is on the earth. Who is he that can intercede with Him except with His Permission? He knows what happens to them (His creatures) in this world, and what will happen to them in the Hereafter. And they will never compass anything of His Knowledge except that which He wills. His Kursiy extends over the heavens and the earth, and He feels no fatigue in guarding and preserving them. And He is the Most High, the Most Great”
[al-Baqarah 2:255]
3 – Reciting “Qul huwa Allahu ahad”, “Qul a’oodhu bi Rabb il-Falaq” and “Qul a’oodhu bi Rabb il-Naas” [i.e., the last three soorahs of the Qur’aan] following every prescribed prayer, and reciting these three soorahs (three times) at the beginning of the day after Fajr prayer, and at the beginning of the night after Maghrib prayer. 
4 – Reciting the last two aayahs of Soorat al-Baqarah at the beginning of the night. These are the aayahs in which Allah says (interpretation of the meaning): 
“The Messenger (Muhammad) believes in what has been sent down to him from his Lord, and (so do) the believers. Each one believes in Allah, His Angels, His Books, and His Messengers. (They say,) ‘We make no distinction between one another of His Messengers’ — and they say, ‘We hear, and we obey. (We seek) Your forgiveness, our Lord, and to You is the return (of all).’
Allah burdens not a person beyond his scope. He gets reward for that (good) which he has earned, and he is punished for that (evil) which he has earned. ‘Our Lord! Punish us not if we forget or fall into error, our Lord! Lay not on us a burden like that which You did lay on those before us (Jews and Christians); our Lord! Put not on us a burden greater than we have strength to bear. Pardon us and grant us forgiveness. Have mercy on us. You are our Mawlaa (Patron, Supporter and Protector) and give us victory over the disbelieving people”
[al-Baqarah 2:285-285]
And it was narrated in a saheeh report that the Messenger of Allah (peace and blessings of Allah be upon him) said: “Whoever recites Aayat al-Kursiy at night will have ongoing protection from Allah and no devil will come near him until morning comes.” And it was also narrated in a saheeh report that the Messenger of Allah (peace and blessings of Allah be upon him) said: “Whoever recites the last two aayahs of Soorat al-Baqarah at night, that will suffice him.” The meaning – and Allah knows best – is that that will be sufficient protection for him against all evil. 
5 – Seeking refuge in the perfect words of Allah from the evil of that which He has created, night and day and when stopping to rest anywhere, be it in the city, in the desert, in the air or on the sea. The Prophet (peace and blessings of Allah be upon him) said: “Whoever stops to rest and says, ‘A’oodhu bi kalimaat Allah il-taammah min sharri ma khalaq  (I seek refuge in the perfect words of Allah from the evil of that which He has created),’ nothing will harm him until he moves on from that place.” 
6 – The Muslim should say at the beginning of the day and the beginning of the night (three times): “Bismillaah alladhi laa yadurr ma’a ismihi shay’un fi’l-ardi wa laa fi’l-samaa’i wa huwa al-samee’ al-‘aleem (In the name of Allah with Whose name nothing on earth or in heaven can cause harm, and He is the All-Hearing, All-Knowing).” According to saheeh reports, the Messenger of Allah (peace and blessings of Allah be upon him) urged us to recite this, and this is a means of keeping safe from all evil. 
These adhkaar and prayers for refuge are among the greatest means of warding off the evil of sihr (witchcraft) and other evils, for the one who recites them regularly with sincerity and faith, putting his trust in Allah and depending upon Him, and being content with that. 
They are also some of the most effective weapons for warding off sihr after it has happened, along with humbly beseeching Allah constantly and asking Him to remove the harm and relieve the distress. Among the du`a’s which have been narrated from the Prophet (peace and blessings of Allah be upon him) to treat diseases such as sihr and other things is the ruqyah by means of which he (peace and blessings of Allah be upon him) used to treat his companions: “Allahumma Rabb al-naas, adhhib il-ba’s, washfi anta al-Shaafi laa shifaa’a illa shifaa’uka shifaa’an laa yughaadir saqaman (O Allah, Lord of mankind, remove the harm and heal him, for You are the Healer and there is no healing except Your healing, with a healing which does not leave any disease behind).” There is also the ruqyah by means of which Jibreel treated the Prophet (peace and blessings of Allah be upon him): “Bismillah urqeeka min kulli shay’in yu’dheeka, wa min sharri kulli nafsin aw ‘aynin haasid Allah yashfeek, bismillaah urqeek (In the name of Allah I perform ruqyah for you, from every thing that is harming you, from the evil of every soul or envious eye may Allah heal you, in the name of Allah I perform ruqyah for you).” This should be repeated three times.
And Allah knows best.