[UKönig]

I will go to my assigned patrol area.
If I run out of ammo before I make it there (has happened), then I will radio BdU and let them know, and they will normally tell me then to 'return to base'. I use the radio first, to make it official. (if they tell me 'keep up the good work', then I continue whatever I was working on last).
I go to my patrol grid and hang out there for 24 hours, then I go pretty much wherever I feel like. And I don't return to base until I am low on or out of ammunition, or damage to the sub makes continuing the patrol dangerous. If you take it upon yourself to return to base without being officially told to, I have noticed a renown penalty is applied. So I try to get word back to the boss and have him tell me what comes next.