Muslims are forbidden altogether to mutilate the dead (Muslim).
Muslims are forbidden to resort to cheating (Muslim).
Children are not to be killed, nor women (Muslim).
Priests and religious functionaries and religious leaders are not to be interfered with (Ôaªavi).
The old and decrepit and women and children are not to be killed. The possibility of peace should always be kept in view (Abu Dawud.
When Muslims enter enemy territory, they should not strike terror into the general population. They should permit no ill-treatment of common folk (Muslim).
A Muslim army should not camp in a place where it causes inconvenience to the general public. When it marches it should take care not to block the road nor cause discomfort to other wayfarers.
No disfigurement of face is to be permitted (Bukhari and Muslim).
The least possible losses should be inflicted upon the enemy (Abu Dawud).
When prisoners of war are put under guard, those closely related should be placed together (Abu Dawud).
Prisoners should live in comfort. Muslims should care more for the comfort of their prisoners than for their own (Tirmidhi).
Emissaries and delegates from other countries should be held in great respect. Any mistakes or discourtesies they commit should be ignored (Abu Dawud, Kitab al-Jihad).
If a Muslim commits the sin of ill-treating a prisoner of war, atonement is to be made by releasing the prisoner without ransom.
When a Muslim takes charge of a prisoner of war, the latter is to be fed and clothed in the same way as the Muslim himself (Bukhari).
The Holy Prophet was so insistent on these rules for a fighting army that he declared that whoever did not observe these rules, would fight not for God but for his own mean self (Abu Dawud).
Abu Bakr, the First Khalifa of Islam, supplemented these commands of the Prophet by some of his own. One of these commands appended here also constitutes part of the Muslim teaching: Public buildings and fruit-bearing trees (and food crops) are not to be damaged (Mu'aÕÕa).
Taken from: http://www.alislam.org/jihad/warandpeace.html