Patrolling - How, when, where, who?

As the topic states, I'm trying to get a feel for patrolling. I know it was used extensively in Dom1 and I have found it to be an incredible boost to quite a few races and initial startups. I use it for nearly every race, only a few don't support INITIAL (Home province 1st turn and on) patrolling well (Abysia for example).

My questions; for those in Dom1 and now in Dom2 are:

1.) How often do you set patrolling?

2.) Why do you set your patrolling?

3.) How much initial population do you sacrifice for patrolling?

4.) What % do you set patrolling to; for what timeframe?

5.) Have you ever set patrol to 200% for the inital 5 turns? If so, why, and what were the results?

The obvious points of patrolling are of course, blood hunting provinces, events and general unrest in kingdoms, how do you use patrolling for that, what type of patrol armies, etc.