There is a great thread on here:
http://www.subsim.com/radioroom/showthread.php?t=229792
which details authentic methods the U-Boot commanders used.
However, in both cases, it relied on getting well ahead of the convoy and lying in wait; the gold standard ideal.
However, what - if any - where the techniques used for shooting at long range or snapshots where you're basically unable due to circumstances to get any real data or recognition, but need to quickly fire and hit?