Well, I start with plotting course towards my patrol grid. As I play stock SH3, my orders are boring - go there and stay for 24hs. Don't know if this is more interesting in GWX.
My route to patrol grid is usually a happy medium between safety and fuel consumption. I travel submerged on 20m during day, I charge batteries on surface during night. I patrol my designated grid once, keeping the pattern - I travel surfaced only during night and chases. However I dive every 60-90 minutes to check hydro manually. If I'm not speeding towards target I usually travel with smallest telegraph speed (3 knots submerged, 5 knots surfaced with charging, 7 knots without charging). Thus I can stay longer at sea, once after 30 days I had still 75% of my fuel!
After leaving my grid I usaually go to zones I expect to find traffic in. I stay on patrol for as long as I have torpedos. Since all I can experience are heavy seas, I don't use my gun. In case of good weather I would go hunting on small merchies with my deck gun.
In my scenario usually one patrol lasts for 30 days or so. That means I don't get as much qualifiqation bonuses as if I would gain with 14-days at sea at a time (after all it's one bonus after every patrol, if this is important for you, you should consider shortening your patrolling time).
Because I have crew fatigue on, I travel with TC higher than 32, usually 64, and 128, if in 1 hour RT I cannot find any target. (on my current patrol it took 10 days of game time until I found something worth a shot, dissapointing - it was German invasion on Norway time, I expected to find some sort of British task force near Bergen
)
I always have a book or a guitar on me, so long no-contacts periods don't bore me
When I'm coming back to Kiel, after reaching Denmark (the year is 1940) I plot a course and set TC for a highest amount possible. Since I read about renown stealing bug, I no longer dock my boat manually, instead I end patrol when I'm 25km from my base.
Take care,
Kubryk