I have completed a DiD career from early '40 to the end of the war in a IID so I know these tactics work
First off know where your enemy is, find the convoy on the hydrophones (or sight if you must...) and put a mark on the map every now and then to work out a rough course.
Once you know where they are and where they're going, just make sure you will end up
in front of them, not coming from behind like you said.
At night (before radar) you could proberly get within 2km of your enemy with a fairly low risk, but during the day you should keep at the maximum sight distance. Even better, just keep out of their sight and follow run parallel to their estimated course.
If you are detected dive deep quickly, always know how deep your boat can go and how deep the water is where you are.
When you hear the pinging it's time to go ahead flank, when you get the 'depth charges in the water' message you should make a ~15* turn to either side (most recommend making hard turns, but it will slow you a lot more).
Once the pinging stops you should change to silent running and set your speed to 2kts, I've heard 2kts is a lot quieter than the 'default' 3, and it seems true in practice.
After that just stay silent and deep, and you should be fine
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This is just how I do it, and it works well for me so you may have some luck with these tactics too. The best teacher is experience
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