Okay...

First of all, don't attack everyone, but try to make them attack you if at all possible. When war starts, always have a diplomat next to rome so you can bribe him to keep pope meter high. If the pope gives you a mission, do it and always try to join and finish a crusade as soon as possible. It doesnt necessarily must be in the levant, but can be eastern european provinces like vilinius or riga which is an easy target for poland/hungary/denmark/HRE or Cordoba for Spanish/Porteguese or Tunis for Milan/Sicily/Venice