The word jihad has been incorrectly translated or rather twisted in order to give the impression that Islam and Muslims are inclined towards violence, that they have a dark side.To really understand the concept of Islamic warfare, it is necessary to know Islamic rules of Jihad. The conditions of Jihad in Islam can be described as under:-

Islam allows fighting only against those oppressors who attack Muslims to force them to convert away from their faith or to drive them out of their homelands.
"Permission to take up arms is hereby given to those who are attacked because they have been oppressed-Allah indeed has power to grant them victory* Those who have been unjustly driven from their homes, only because they said: "Our Lord is Allah" (22:39-40)

"And how could you refuse to fight in the cause of God and the utterly helpless men and women and children who are crying: O our Sustainer! Lead us forth (to freedom) out of this land whose people are oppressors..." (4:75)

"Allah does not forbid you to deal justly and kindly with those (unbelievers) who do not fight you on account of your faith nor drove you out of your homelands. Verily Allah loves those who deal with full equity

God only forbids you to turn in friendship towards those who fight against you because of (your) faith, and drive you forth from your homelands, or help (others) in driving you forth; and as for those (from among you) who turn towards them in friendship, it is they, they are truly the wrongdoers" (60:8-9)

Islam strictly forbids aggression in the battle field and excesses of any kind
"And fight in God's cause those who wage war against you, but do not commit aggression for verily God does not love aggressors" (2:190)
This means that a) the distinction between combatants and non-combatants and respect for those who are no longer engaged in the battle-the dead, the wounded and the prisoners- and neutralization of medical personnel and supplies; and b) no use of treacherous means of weapons of mass and indiscriminate destruction.

The Prophet commanded that the life of civilians, foliage, livestock, clergy, and places of worship are to be protected. The same message was carried out by the Prophet's successors. For example, we have the record of what Abou Bakr the first of the Rashidun Caliphs said to his army before they departed for battle [4]:
"Stop, O people! That I may give you ten rules for your guidance in the battlefield. Do not commit treachery or deviate from the straight path. You must not mutilate dead bodies. Do not kill a child, or a woman, or an elderly man. Bring no harm to the trees, nor burn them with fire, especially those which are fruitful. Do not slay any of the enemy's folk, except for food. You are likely to pass by people who have devoted their lives to monastic services; leave them alone".
If the enemy inclines to peace, peace should be accepted, even at the risk of possible deception by the enemy.
"But if they incline to peace, you also incline to it, and (put your) trust in God, verily He is all-Hearing and all-Knowing* And if they intended to deceive you, then verily, God is all sufficient for you..." (8:61-62)

The dignity and sustenance of the prisoners of war should be guaranteed.
"And who give food-however great be their own want for it-unto the needy, the orphan and the captivity of war (saying in their hearts) ‘We feed you for the sake of God alone. We desire no recompense from you, or thanks'" (76:9-11)
Observance of treaties and pacts is stressed in the Quran. When some Muslims were still in Mecca and they could not migrate to Medina, the Quran stated:

"And to those who accepted faith but did not migrate (to Medina), you owe no duty of protection to them until they migrate; but if they seek your help in religion, it is your duty to help them except against people with whom you have a treaty of mutual alliance; and Allah is the all-Seer of what you do" (8:72)

Freedom of religion is fundamental to Islamic principles; therefore non-Muslims cannot be forced to accept Islam:
"Let there be no compulsion in religion; truth stands out clear from error; whoever rejects the powers of evil and believes in God has grasped the most trustworthy handhold that will never breaks. And God hears and knows all things." (2:256)
"If it has been your Lord's will, they would all have believed (in God's message), all those who are on earth. Will you then compel people against their will to believe? (10:99)
"And you (Muhammad) can by no means force them to believe; just remind them through the Quran such as they may fear my warnings" (50:45)

Suicide for any purpose is prohibited in Islam. Quran says, “Do not put yourself to destruction with your own hands” (2:195). A Tradition of the Prophet Muhammad says, “And if somebody commits suicide with anything in this world, he will be tortured with that very thing on the Day of Resurrection.” Suicide bombing involves killing oneself as well as others. So it is doubly condemned.

please tell me the conditions for jihad

According to Islamic beliefs .Jihad can only be approved by head of state.