Short answers, pulled from the story.
Pope Urban II declared the First Crusade on the 27th of November 1095. This declaration occurred before a crowd at the Council of Clermont in France and promised spiritual rewards for recovering Jerusalem from Muslim control.
Godfrey of Bouillon, Duke of Lower Lorraine, led the Princes' Crusade which departed for the Holy Land in August 1096. His army numbered between 60,000 and 100,000 men including up to 7,000 knights.
The Second Crusade failed because Damascene raids and news of Nur al-Din's approaching reinforcements forced the crusaders to abandon the siege beginning on the 24th of July. The German army had already been crushed by Mesud's forces at the Battle of Dorylaeum on the 25th of October 1147.
Richard I secured Frankish control of the coast between Tyre and Jaffa through the Treaty of Jaffa signed on the 2nd of September 1192. This agreement followed his victory over Saladin at the Battle of Arsuf and the capture of Jaffa from Acre.
The Fourth Crusade was diverted when Alexios Angelos offered to reunite the Byzantine Church with Rome if restored to Constantinople. Leaders accepted this proposal while wintering in Zara despite papal prohibition and having recently attacked a Christian city.
Jerusalem was returned to Christians via the Treaty of Jaffa on the 18th of February 1229. This treaty ceded Jerusalem, Bethlehem, and other key cities to Christians while preserving Muslim places of worship.