Edit:
Let me post something that is usefull:
When you get a contact report and want to sink it using manual targetting you could use this guide as a reference:
http://www.subsim.com/radioroom/showthread.php?t=88961
Hydrophone intercepting method without using any map tools:
When the contact comes closer you have to listen to the bearing change and adjust your own course/speed accordingly until the contact bearing stays the same.
Sometimes the contact is out of reach and you won't get a new contact for week. That's unfortunate, but those things happen.
Now you can play at a 100% realism. Gute Jagd