According to Imam Hasan bin Ali Al Askari (as) The signs of a true believer are five:-

1) Recite 51 Rak—a’t Salaat during the 24 hours of the day (17 Rak—a’ts obligatory, + 34 Rak—a’ts in Naafilah Salaats).

2) Be in Karbala for Ziyarat of Imam Husayn (as)/other martyrs, or at least recite Ziyarat of the Holy Imam as given below

3) To wear a ring in the right hand.

4) To put the forehead on the earth (preferably on the earth of Karbala) in prostration.

5) To pronounce “Bismillahir-Rah’maanir-Rah’eem” in clear and loud voice while praying the salats.

The Purpose of Imams mission is very well summarised in this ziarat as "...made every effort and put his heart, mind, soul and life at the disposal of Thy mission to liberate the people from the yoke of ignorance"

It reads:

Peace be on the favorite of Allah,  Peace be on the beloved friend of Allah, His distinguished hero! Peace be on the choicest confidant of Allah, sincerely attached precisely like his father! Peace be on Hussain, who gave his life in the way of Allah, a martyr, underwent untold hardships Peace be on the hostage surrounded by the-tightening circle of sorrow and grief, killed by a horde of savages.

O my Allah I give witness that beyond a shadow of doubt he is Thy favorite and choicest confidant, who enjoys Thy confidence and favor, precisely like his father!
Thou looked upto him and elected him in Thy cause, picked and chose him for the good fortune, selected for him the best purified parents, appointed him guardian, leader, and defender of rights, a true representative (inheritor and progenitor) of guardians, leaders and defenders of rights, gave him much and more from the inheritance of the Prophets, put him forward as a decisive argument, along with the other successors (of the Holy Prophet-the twelve lmams) to the mankind. He met with deadly dangers, acted justly and fairly, made use of everything belonging to him to pay full attention to give sincere advice, took pains, made every effort and put his heart, mind, soul and life at the disposal of Thy mission to liberate the people from the yoke of ignorance and evil of bewilderment, but an evildoer, deceived with empty hopes of mean and worthless worldly gains, had pressed heavily on him, and sold out his share (eternal bliss) for the meanest and lowest bargain, betrayed his "day of judgment" for a vulgar return, took pride in insolence, fell into the fathom- well of silly stupid follies, provoked Thee and Thy Prophet to anger, did as the harsh discordant, the hypocrite, the heavily burdened bearers of sin, condemned to Hellfire, advised to him, however, he (the Holy lmam), steadily, rightly and justly coped With them, till, in Thy obedience, gave his life after which his family was set adrift.
 
 

O my Allah, therefore, condemn them to hell as a denunciation and conviction; and crack-down on them with a painful Punishment. Peace be on you O the son of the Messenger of Allah! Peace be on you O the son of the first of the successors (of the Holy Prophet)! I bear witness that Allah put faith in you like He had full confidence in your father, and that you always looked for and collected good and virtue, lived a highly praiseworthy life and departed from this world a martyr, forsaken and abused; I bear witness that Allah will promptly fulfill the promise, He made to you, and destroy those who left you helpless and punish those who killed you; I bear witness that you kept your promise made with Allah, and strived in His way till what was certain came upon you, so curse of Allah be an those who killed you, curse of Allah be on those who oppressed you, curse of Allah be on the people who came to know and approved.

O my Allah be my witness that I make friends with those who love him and oppose those who deny him. I, my father and mother, are at your disposal 0 the son of the Messenger of Allah. I know and bear witness that you were "light" in the sublime loins and in the pure wombs, never touched you the dirt of ignorance, nor ever obscurity concealed you in its folds;I bear witness that you are the pillar of "Deen", support of the Muslims, refuge of the faithful; I bear witness that you are a truthful, well-aware, content, intelligent, rightly guided guide (Imam); I bear witness that the Imams among your descendants are the symbols of "conscious piety" and signs of "true guidance",

  the "safe handle"-Islam, and the decisive arguments over mankind; I declare positively that I have full faith in you and I know for certain that you shall return. I am, fully committed to the laws of my religion, certain of my deeds, my mind and heart ready for your return, and my affairs carried out in the light of your instructions, till Allah gives you permission, together with you, along with you, not at the same time with your enemies. Blessings of Allah be on you, on your souls, on your bodies when you are visible, when you are invisible, on your perceivable aspects, on your innermost genius be it so, O Lord of the worlds