Here is a short version of how XP generation and passup works, followed by a link to the leadership/loyalty article people seem to reference more than any other.
XP from your vassal
As your vassal hunts, a certain percentage of the XP generated gets passed into the allegiance system. That XP goes into a "pool" that is periodically emptied into your patron's XP (it isn't real-time transfer of XP to your patron). The patron's leadership skill determines how much of the XP in the pool is transferred to the patron. The amount ranges from 68% to 125%. With an effective leadership of 163, you will pull 125% of the XP
That’s what you GET from your vassal. The most you can pass UP from your vassal is 75% of what you get. I know it’s weird. The most XP you can pass through from your vassal to your patron is 93.75% (125% times 75%). With an effective leadership of 200, you will pass up 75% of what you get from your vassal.
So, with an effective leadership of 163 and an effective loyalty of 200, you will automatically passthrough 93.75% of the XP you receive from your vassals.
XP generated from hunting
As you hunts, you will put a percentage of the XP you earn into the XP pool for your patron. This XP is extra, it doesn’t come out of your XP at all. This is the XP that the 19%, or 25%, or whatever is referring to in the posts above this one. Basically, the higher your loyalty is, the higher percentage of XP you pass up from your hunting. That also means that as you raise your loyalty, you don’t have to hunt quite as hard in order to make quota. Supposedly the minimum amount of XP you can pass up is 8.9% of what you earn from hunting. The actual percentage is what people don’t seem to agree on. I have heard for a long time that typical pass up rates are 20% - 25%, and that pass up rates can go as high as about 40%, depending on certain factors.
The URL here
http://www.allglobaltravel.com/dkod/lead_loyal.htm is a copy of Oberion’s original essay on Crossroads of Dereth. I can’ get to CoD from work because of the firewall, so this is the link you get.

It has all of the nauseating details of how all of this stuff is figured out.