It begins when the person likes something, then his evil soul dwells on the matter, and by continually looking at the person who has the thing of which he feels jealous, he directs his spell towards him.
Late Shaykh Abbas Qummi (may Allah bless him) has recommended the recitation of verse 51 of chapter al-Qalam to ward off the spell cast by the evil eye. Given the circumstance in which the verse was revealed, reciting it is good. In addition to this verse, reciting other verses of the Quran such as Sura "al-Nās", "falaq", "al-Hamd" and "al-Tawhid" have been recommended for protecting oneself against the evil eye.
The evil eye is a part of the influence of the soul. There is no reason to negate it as it has occurred repeatedly in the concrete external world. There are some traditions which explicitly state that the influence of an evil eye is real. It is narrated from Durr al-Manthur that the Holy Prophet said: "The influence of an evil eye is a fact..." He also said: "An evil eye puts a healthy man into the grave and a perfect camel into the caldron."
The Commander of the Faithful, Ali (a.s.) said: "The Holy Prophet (pbuh) took amulet (prayers or supplications which a person keeps with him to ward off the curse of an evil eye) for Hassan and Hussein (a.s). He then read the dua:
«أُعِیذُکُمَا بِکَلِمَاتِ اللَّهِ التَّامَّاتِ وَ أَسْمَائِهِ الْحُسْنَى کُلِّهَا عَامَّةً مِنْ شَرِّ السَّامَّةِ وَ الْهَامَّةِ وَ مِنْ شَرِّ کُلِّ عَیْنٍ لَامَّةٍ وَ مِنْ شَرِّ حَاسِدٍ إِذَا حَسَدَ »
[I seek refuge for you in God's words and all His attributes from the evil of everything that causes affliction and from the evil all invisible things and from the evil of every laammah (evil) eye and from the evil of the envious when he envies. ]
Then the Prophet (pbuh) told us: "Ibrahim sought amulets for Ismail and Ishaq as such." 
It is mentioned in al-Hikmah (saying) 400 of Nahjul Balaghah that: "The influence of the evil eye is a fact and seeking dua for protecting oneself against it is also a fact."
It is understood from the above narrations that the influence of the evil is not an illusion or a superstition; rather it is a reality that takes place in the external world and there are protective measures available for guarding oneself against it.
It is well-known that verse 51 of chapter al-Qalam is effective for warding off the spell cast by the evil eye. In this verse, God, the Exalted says to the Holy Prophet (pbuh): "And those who disbelieve would almost smite you with their eyes when they hear the reminder, and they say: Most surely he is mad."
It is said that this verse was revealed when a man from Bani Asad tribe suffered hunger for three days. Thereafter, whenever he confronted anything he would say: "As of today, I have not seen anything like that" and that thing would suddenly break or get damaged somehow. Some people wanted to do the same thing to the Prophet (pbuh) but Allah, the Almighty, protected him against it.'
Late Allamah Tabatabai (r.a.) says in the commentary of the foregoing verse: "The Arabic word 'leyuzlequnak' in the verse, as per the saying of all commentators, refers to smiting someone with one's eye or casting an evil eye on someone which is by itself an effect of the soul and there is no rational proof to refute its existence. In fact, many incidents have been seen in the outside world which can be the effects of the evil eye. We have no reason to deny it or reject it as a superstitious belief."
Zamakhshari narrates from Hasan al-Basri (one of the prominent Sunni figures) that reciting the aforementioned verse for warding offer the spell of the evil eye is recommended.
Late Shaykh Abbas Qummi, the famous Shia narrator and author of Mafatihul Jenan, says in his explanation concerning charms and amulets that reciting the verse "wa ein yakadul-lazina kafaru" is good and may be recited for warding off the influence of the evil eye.
It should be noted that the narrations mentioned under this verse in various commentaries do not make mention of warding off the danger of the evil eye through this verse.
Late Allamah Majlisi (may Allah be pleased with him) relates a narration from Imam Sadiq (a.s.) about warding off the influence of the evil eye. Imam Sadiq (a.s) said: "He who is afraid lest his eye may influence another person or another person's eye may influence him should recite three times "Ma sha'allahu la quwata illa billahil aliyil azim" or he should recite "qul a'uzu bi-rabbinnas wa qul a'uzu birabbil falaq". In another tradition, Sura-e al-Hamd and Sura-e al-Tawhid have been added. However, when he explains these treatments, he does not make mention of the verse under discussion.
Based on the above, what is certain is that there have been instances of afflictions concerned with the influence of the evil eye and that there are also certain du'as (supplications) which have been recommended for protection against the influence of the evil eye.
For further information, vide Tafsir Nomouneh, vol.24, pg.426.
 - Durr al-Manthur, pg.651.
 - Al-Kafi vol.3, pg.569, hadith: 3. The Arabic version of the hadith is the following:
عَلِیُّ بْنُ إِبْرَاهِیمَ عَنْ أَبِیهِ عَنْ بَعْضِ أَصْحَابِهِ عَنِ الْقَدَّاحِ عَنْ أَبِی عَبْدِ اللَّهِ ع قَالَ قَالَ أَمِیرُ الْمُؤْمِنِینَ ع رَقَى النَّبِیُّ ص حَسَناً وَ حُسَیْناً فَقَالَ أُعِیذُکُمَا بِکَلِمَاتِ اللَّهِ التَّامَّاتِ وَ أَسْمَائِهِ الْحُسْنَى کُلِّهَا عَامَّةً مِنْ شَرِّ السَّامَّةِ وَ الْهَامَّةِ وَ مِنْ شَرِّ کُلِّ عَیْنٍ لَامَّةٍ وَ مِنْ شَرِّ حَاسِدٍ إِذَا حَسَدَ ثُمَّ الْتَفَتَ النَّبِیُّ ص إِلَیْنَا فَقَالَ هَکَذَا کَانَ یُعَوِّذُ إِبْرَاهِیمُ إِسْمَاعِیلَ وَ إِسْحَاقَ (ع).
 - Nahjul Balaghah pg.547 : العین حق والرقی حق
 - Al-Qalam: 51 وَ إِن یَکاَدُ الَّذِینَ کَفَرُواْ لَیزُْلِقُونَکَ بِأَبْصَارِهِمْ لَمَّا سمَِعُواْ الذِّکْرَ وَ یَقُولُونَ إِنَّهُ لمََجْنُونٌ Tafsir al-Mizan, Allamah Tabatabai, vol.19, pg.636.
 - Al-Kashshaf, Zamakhshari, vol.3 and 4, pg.1278, Darul Haya Publications.
 - Al-Mizan, vol.19, pg.648.
 - Al-Kashshaf, Zamakhshari, vol.3 and 4, pg.1279.
 - Al-Qalam: 51
 - Shaykh Abbas Qummi, Mafatihul Jenan, pg.319. (He has not made any mention of this verse in regards to the evil eye in Safinatul Behar.]
 - Tafsir al-Mizan, vol.19, pg. 651; Tafsir Nasim Rahmat, pg.71; Tafsir Noor al-Thaqalain, vol.5, pg.400; Tafsir Nomouneh, vol.24, pg.426.
 - «ماشاء الله لاقوة الا بالله العلی العظیم»
 - Hilyatul Muttaqin, Allamah Majlisi, pg.319, Hijrat Publication