One of my sub-goals in any game is getting a position that allows me to refuse crusades. Either overwhelming force (takes awhile) or a good choke-point where they try to funnel through.

It was mentioned somewhere that getting a string of ships to the Holy Land reduces "hang-time" because crusades can get to destination. Sometimes this works...but if the crusade is defeated (or is not terribly brave) it just sits in your port.