“Adhaan” in Arabic means conveying. The "Adhaan" is a call to inform others in specific words that the time for a particular prayer has begun. It is a call to the congregation and is an expression of the Islamic practice. It is required as an act for all the Obligatory Prayers.
The word adhaan in Arabic means announcing or proclaiming.
In Islam it means announcing that the time (for prayer) has come. It was prescribed during the time of the Messenger of Allah (peace and blessings of Allah be upon him) in Madeenah.
‘Abd-Allah ibn Zayd ibn Abd Rabbihi, when the Messenger of Allah (peace and blessings of Allah be upon him) decided to use a bell even though he disliked it because it was like what the Christians used, ‘there appeared to me in a dream a man who was wearing two green garments, in whose hand was a bell. I said, “O slave of Allah, will you sell that bell?” he said, “What will you do with it?” I said, “We will call the people to prayer with it.” He said, “Shall I not show you something better than that?” I said, “Yes.” He said, “Say, Allahu akbar Allah akbar … (to the end of the adhaan).” When morning came, I went to the Messenger of Allah (peace and blessings of Allah be upon him) and told him what I had seen. He said, “This is a true dream, in sha Allah. Get up with Bilaal and tell him what you have seen, so that he can give the call, because he has a more beautiful voice than you.” So I got up with Bilaal and started telling him what I had seen, and he gave the call to prayer. ‘Umar ibn al-Khattaab heard that whilst he was in his house, and he came out, dragging his cloak behind him, saying, “By the One Who sent you with the truth, O Messenger of Allah, I saw the same as he saw.” The Messenger of Allah (peace and blessings of Allah be upon him) said: “To Allah be praise.”’ (Narrated by Ahmad, 1588; al-Tirmidhi, 174; Abu Dawood, 421, 430; Ibn Maajah, 698). This hadeeth was classed as saheeh by Ibn Khuzaymah, 1/189; Ibn Hibbaan, 4/572; al-Albaani in Tamaam al-Minnah, p. 145.
the words of the adhaan came in a dream which was seen by a great sahaabi and approved of by our great Prophet. They were not a suggestion as you mentioned, but a dream, and it is known that dreams are one of the seventy parts of Prophethood, because it was stated in a hadeeth narrated by Ibn ‘Umar that the Prophet (peace and blessings of Allah be upon him) said: “Dreams are one of the seventy parts of Prophethood.” (Narrated by Ahmad, 4449).
Al-Bukhaari narrated a different version: “True dreams are one of the forty-six parts of Prophethood.” (Narrated by al-Bukhaari,, 6474; Muslim, 4203, 42005). 
Preferably, there should be an appointed Muadhin(who gives Adhaan) at each Masjid who will call the people to prayer when the time of a particular prayer is due. In performing the Adhaan, the Muadhin would stand facing the direction of the "Qiblah" (towards the sacred masjid in Makkah). He would then raise both hands up to his ears and say in a loud voice the following words:
1. ALLAHU AKBAR - Allah is the greatest (to be repeated 4 times).
2. ASH-HADU ANLA ILAHA ILLALLAH - I testify that there is no god but Allah. (to be repeated 2 times).
3. ASH-HADU ANNA MUHAMMADAN RASUULULLAAH - I testify that Muhammad is Allah's messenger. (to be repeated 2 times).
4. HAYYAA LAS SALAAT - Come fast to prayer. (to be repeated 2 times). The Muadhin, when reciting this turns the face slightly to the right side.
5. HAYYAA LAL FALAAH - Come fast to success. (to be repeated 2 times). The Muadhin, when reciting this turns the face slightly to the left side.
6. ALLAHU AKBAR -Allah is the greatest. (to be repeated 2 times).
7. LAA ILAHA ILLALLAH - There is no god but Allah. (to be recited once).
Note : In the Adhaan, for the Fajr (Dawn) prayer, the following words are recited twice after Hayya'alal Falaah: ASSALATU KHEIRUM MINA NAWM , (to be recited two times) which means - " Salaat is better than sleep ". 
Upon the completion of the Adhaan, it is recommended that the listener recite the following supplication: ALLAHUMMA RABBA HADHIHID DA'WATI - TAMMAH, WASALATIL QA'IMAH, ATI MUHAMMADAN AL WASILATA WAL FADHILATA, - WAAB'ATHUHU MAQAMUM MAH- MUDAN-ALLADHII WAAD TAHU, which means: "O Allah, Lord of this complete call and of the prayer to be held, grant Muhammad the most favored and excellent position in the Paradise and raise him to the praise worthy place that You have promised him".
The greatness of the virtue which Islam attaches to the "Adhaan" and the one who performs it i.e. the "Muadhin", can be noted from the following verse of the Qur'an:“ Who is better in speech than one who calls (the people) to allah and works righteousness” (Qur'an 41:33). 
This ayath concerns and refers to the Muadhin and was revealed on no other reason than for the Muadhin. 
And, from the prophetic traditions, Abu Hurairah reported that the Prophet (peace be upon him), said:“ If the people knew the reward in the Adhaan and the first row of the prayer and that they could not get it (the reward) save by drawing lots, they would draw lots” Sahih Al Bukhari Vol 1:589
  http://islamqa.info/en/ref/7945