The word "Muslim" means one who submits to the will of God. The first principle of Islam is known as the Shahaadah(Testimony of Faith), and is as follows:
Kalimah Shahaadat:
Ash-hadu-an-la-lillah-illal-lahu-wahdahu-lashareekala-hu-wa-ashad-anna-Muhummad-an-abdu-hu-wa-rasoolu-hu.
(This is giving a verbal agreement in front of other people that you believe and give testimony that there is only ONE God (Allah s.w.a.) and that Prophet Muhammad p.b.u.h. is the Prophet and Messenger of Allah s.w.a.)
In a broader sense, anyone who willingly submits to the will of God is a Muslim. Thus, all the prophets preceding Prophet Muhammad, 
, are considered Muslims.
, are considered Muslims.
One cannot judge Islam by looking at those individuals who have a Muslim name, but in their actions, they are not living or behaving as Muslims. Muslims are ordinary people like other humans; among them are the good and the bad. They are not infallible creatures and, therefore, make mistakes.
When we mention the characteristics of a Muslim, we do not assume that all Muslims have these characteristics, but only those who follow -- to the best of their abilities -- the teachings of Islam.
We can thus summarize the teachings of Islam about the Muslim character concisely in the following way:
A Muslim is truthful, not dishonest
He is humble, not arrogant
He is moderate, not an extremist
He is reserved, not garrulous
He is soft-spoken, not boastful
He is loving and solicitous to others, not unmindful of them
He is considerate and compassionate, not harsh
He is polite and helpful, not insulting and disrespectful to people
He is generous and charitable, not selfish and miserly
He is refined and gentle in speech, not prone to swearing or cursing
He is cheerful and generous, not bitter and resentful
He is grateful for what he has, not ungrateful
He is cheerful and pleasant, not irritable and gloomy
He is chaste and pure, not lustful
He is alert, not absent-minded
He is dignified and decent, not graceless
He is sincere and straightforward, not hypocritical
He is optimistic and hopeful, not cynical or pessimistic
He is confident and deep in faith, not doubtful and wavering
He is spiritually oriented, not materialistic
He always has faith in God’s mercy, not losing heart or becoming desperate
He is diligent and vigilant, not negligent to his duties
He is thankful to God and constantly prays to Him, not forgetful of His innumerable blessings.
Five Pillars of Islam Muslim has to follow
FIVE PILLARS OF ISLAM
The foundation of Islam are five:- Bearing witness that there is no god but Allah and that Muhammad is the Messenger of Allah,
- observance of 5 times Prayer,
- Paying Zakat,
- Fasting during Ramadan,
- And Pilgrimage to the house of Allah (HAJJ). Read More...
Things Essential For a Muslim to Believe In
IMAN-E-MUJMAL (The Summary Declaration of Faith)
(Aamantu billah kama huwa bi asmaa i hi wa sifaatihi wa qabiltu jamee'a ahkaamihi)
I have faith in Allah as He is known by His Names and attributes
and I accept all His commands.IMAN-E-MUFASSIL
(The Detailed Declaration of Faith, A Muslim has to proclaim Faith in 7 things, these are:)
(1,Aamantu bilLahi 2,wa Malaikatihi 3,wa Kutubihi 4,wa Rasulihi 5,wal Yawmul Akhirihi 6,wal Qadri khairihi wa sharrihi minALlahi Ta'ala 7,wal ba'thihi Ba'adal Mawt.)
1, I have faith in Allah
2, and His Angels,
3, His Books
4, and His Messengers,
5, and the Day of Judgement
6, and that all good and evil and fate is from Almighty Allah
7, and it is sure that there will be resurrection after death **
Did you Preach and Propagate ISLAM today?
Did you Preach and Propagate ISLAM today?