Here are a few points yanked straight from Davebaby's Guide To Guilds:
Templars Chapter Houses are restricted to catholic factions only (excluding HRE, Spain and Portugal).
St. John’s Chapter Houses are restricted to catholic factions only (excluding HRE, Spain and Portugal).
Teutonic Knights Chapter Houses are restricted to the HRE only.
Knights of Santiago Chapter Houses are restricted to Spain and Portugal only.

To Gain Crusader Knight’s Guild Points:
General joins crusade: +25 all settlements
General abandons crusade: -25 all settlements
Recruit Specialist Knight: +10 settlement, +1 others (knight type tied to guild type)
Governor Chivalry >4: +5 settlement (per turn)

St. John's guild get a +10 settlement, +1 others bonus when the settlement has muslim neighbours (for each settlement, each turn)
St. John's guild get a +10 bonus for all settlements when you declare war on a muslim faction.
Teutonic guild get a +10 settlement, +1 others bonus when the settlement has pagan neighbours (for each settlement, each turn)
The whole guide can be found here: https://forums.totalwar.org/vb/showthread.php?t=75649

So yeah to get Templar you can join up a lot of generals to go crusading, or if you're a little more patient/sane you can park a high chivalry general in the castle (they're castle only) you want the chapter house in, and wait for him to build up the points for you (5 every turn). Probably doing them in combination is the best. If you get offered the wrong chapter house, just reject it, you should be very near (if not at already) enough points for the one you want, which should be offered soon. You should also note that you may only have one type of them in your entire empire (except if you capture them, I suppose), so don't take Templars if you really want St. Johns, and vice versa: you can't get offered the other once you take one.