I have some exploits for you....
These are from a previous post, so I am cut and pasting to make it easier on me. Ignore something if its not relevant.

"As France, I have become an expert crusader. France starts out with quite a few generals, and once I get a diplomat to Rome and nab "modern day" france as a base of operations, I lump all my generals together and persuade the pope into a crusade of my choice. Generally, any catholic faction that has been excommed is your target. Barring that, a distant Muslim province that has several rebel/non cath regions in between allows you to get a nice swath of destruction on the way there.

With all my generals in one stack, I join a crusade. Then, I abandon the crusade. Then I join the crusade. Over and over, again and again, until the general leading the expedition has "the saint" after his name.

Then I rinse and repeat for all the generals in the stack.

Then I remove all the generals, save one, and send the crusading army on it's way.

With the rest of the generals still in "crusade" mode, but with no accompanying troops, I return them to my best castles and towns as governors.

The chivalry bonus makes this all worthwhile, because your towns will explode with population and your castles will be ready for improvement faster.

Then, build up some troops at home.

Next, let one of your (still technically "crusading") generals move to the middle of your territory, and send some of your best (and most expensive) troops to join him

Then, when you're ready, hit the leave/join crusade button twice. Boom, all of your troops have joined the crusade.

Now repeat the process until most of your generals are on a long crusade eliminating a catholic faction that has been excommed or into muslim territory, or my personal preference, through Byzantine territory and Turkey.

For non catholic factions, exterminate the populace to maintain order. build a church the first turn, and then pop out as many priests as possible.

Bonus here being, not only will you convert the populace faster, but you will get several cardinals. Next papal election is pwned by you.

sacking cities while crusading is easy, just make sure you're traveling in a straight line as best you can towards your target, and end your turn much closer to it, and end the turn besieging the city. Sack it next turn, leave a garrison, and move quickly forward.

In 30 turns I eliminated the HRE, Turkey, and Byzantium, and made it all the way to Baghdad. I have about 15 generals with 5 or above chivalry, and a massive army sacking the entire middle east.

I generally prefer keeping my reputation honorable until I am vastly superior to all my neighbors in terms of immediate "blitz and sack their territory" ability. Then, without warning, I amass about 3 full stacks or more, and attack on multiple fronts and end the war as quick as possible.

Note that when you are a lone general on a crusade, you can move in ANY DIRECTION and not lose troops (your body guard will remain the same size).

Use this technique to move your general far away from the crusading target (say, Scotland or Russia or Africa)

Once there, recruit as many mercenaries as possible and sack all surrounding cities on your way towards the "target" of the crusade.

I think the crusade concept means the catholic factions are overpowered. If you had to pay for the troops you recruited (say, maybe at half the maintenance cost) it would be realistic. This way you can't have 25 stacks completely full on crusades and still be making 10000 florins per turn.
Note well-
I have been informed that apparently, the 5 chivalry exploit for crusades does not work after patch 1.2

So tough luck all you patch users. I guess now all you can do is build dozens of free full stack armies and also send crusading generals in any direction and leave crusading generals inside cities so that if you need an instant army for an upcoming battle you can leave the city and hire a bunch of crusader mercs and kill whatever approaches you.

Crusades... are... still overpowered!"

Pretty much the way to win is the expert use of crusades and jihads. As Britain, I own all of the British Isles, Spain, France, and northern Africa... on TURN 25. I have about 10 full stacks that just finished crusading, and I am about to mop up the Germans.

You can use 'house rules' to make the game easier if you want a challenge, but these methods assure quick expansion.

Oh, by the way, ANOTHER exploit…

Leave/Join crusade every turn for all crusading generals at the end of their turn, until the 10 turn limit for joining expires. Why?

YOU NEVER LOSE TROOPS TO DESERTION IN ANY DIRECTION YOU TRAVEL.

Pwned!