I always use crusades as part of an overall plan. I always check that my King can take the influence hit if it goes wrong. I top up the crusade with mercs and the odd prince to ensure a good leader and I always support the crusade with other armies. If I can hoover some other factions troops up, all well and good.
From a role playing point of view I try to avoid unhistoric Crusades, so they are mainly aimed at the middle east - but I have been known to visit other parts!!
If you are a Catholic faction and especially if you are a Holy order or historically a crusading nation such as the English or French, then I think you should indulge as soon as possible, it is all part of the game.
The one thing I don't tend to do is whip up Zeal in front of a Crusade, but that is because I tend to not put a lot of effort into the religious side of the game.