A. Check the description of Hoar on the player wiki. Gives a pretty basic description of the Church, it's basis and followers.
As for followers of Hoar, it can range accordingly. Anywhere from remorseless bounty hunters to a strict morality based Man of the People. As far as I am aware, the church is a loosely bound organization, shrines should be considered a church. Unfortuneatly my PC never did build a shrine himself, but it was on the agenda.
Vengance is set accordingly....followers of Hoar walk a very fine line in their own service...some set vengence upon the target with the intention of the target living but suffering. Others of a darker path will kill slowly...and others will slit a throat for the right price.
It isn't uncommon for the followers to wear trophies upon a red sash....a finger, or perhaps the vial that contained the poison that the assassin used to poison the local well (the same water you gave to him when posing as a bartender after you bribed the bartender to leave his station for an hour or two) and so forth.
My own PC was a ranger turned cleric of Hoar, unfortuneatly I didn't get too far into the cleric phase before he bit it.
My own PC background was a slaver hunter....my Favored enemy humans, so he definately had a grudge against the Zhents he met in his time...honestly, my own PC never got to exact too much vengance....the first real attempt at it saw him dead. Hope this helps you a bit.
Oh, the petitioning part I enacted at midnight, even before the cleric level I prayed to let Hoar guide my blades to their true targets ect.
Here are my library entries for that PC if you are interested.
http://www.alandfaraway.org/phpbbforum/ ... hp?t=33202
Wish I could tell you a bit more what he was like, but I'm sorta out of that PC now...