Through My Career I have been trying different approaches. As warhawk has said, going below the thermal layer and waiting for that can to pass works well, and is one I have been using. I keep my scope down as much as possible and pop it up for quick peeks to see what is going on. I used to leave it up, but it draws way too much attention.
One very interesting patrol I was running low on batteries after a photo recon mission. It was either try and recharge the batteries or go nowhere. My only problem was this pesky sub chaser that was on me like white on rice. I waited till night time so the chance of an air attck was nil, I emergency surfaced, hoped on the 40 MM and started shooting until I was able to hop on the deck gun. I manned up the deck gun and started pounding the sub chaser who was coming head on. I destroyed his bow mount (he did get a hit on me prior), his stack was blown off and the ship was then destroyed and headed to davey jones's locker. I never use the surface and fight tactic (the only time I will surface would be for the lone merchant who I can shoot at long distance if the fish attack went unsucessful), but this time It was my only option and the battle was filled with so much suspense. After the sub chaser was destroyed I let out a cheerful yell and was overwhelmed with joy and relief.
My work however was not finished and I set a small perimeter out of the range of the ships and sailed around until I had just enough battrey to high tail out of there.....well not high tail, more like 1 KT. The trip was extemely long but worth it as the USS Balao and her crew would live to fight another day
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Everyone has their own tactics, many share similar ones. Use them as you please and learn from others success and failure, as not knowing of ones failures can cheat you of valuable knowlege.