[Warren Peace]

I can only speak for early war ('39-'40) with Type VII's and Type IIs, but I have a few favorite areas that I spend quite a bit of time in.

If you're driving a Type II (I can't explain it, but I love being in a dug-out canoe), there's a passage just to the north-east of Scapa Flow that is fairly active (AN14 if memory serves). I usually spend a few days up there, then work down the eastern coast of Britain before heading back to Kiel (Lots of single merchants along the coast line).

If I'm cruising in a Type VII, I like going up over the top of England and working down the western coast of Ireland. The north-west and south-west areas around the island have contacts out the wazoo (I believe that between the two areas, there's something like 3 single-merchant lanes and 4 convoy lanes).

As for tactics, while patrolling I rarely go above 1/3rd. I'd rather spend more time on station, allowing for contacts to come to me, then burn my fuel out hoping to run into one. Also, running submerged at 1/3rd gives a good amount of time below the surface and is fairly quiet, so good hydrophone range without having to continually change the engine speeds.
I concur with checking the hydrophones at least twice a day (I usually do 3-4 checks, depending on where I am and what the weather is like. If the weather is terrible, I end up spending more time under water than I do on the surface). And you should definitely do an occasional sweep of the hydrophones yourself (default key is 'H'). You can adjust the volume also, the little black knob to the lower right, clicking on different areas raises/lowers the volume.

The only time I run faster is if I'm en route to my patrol/home, running down a contact, or trying to get out of dodge. Slower patrol speed means more fuel for running flank on a contact to get into the perfect ambush position.