Torpedo hunting is one of the most difficult aspects of SL. It just takes practice. The best hints I can give are 1.) take a fast ship or plenty of afterburner fuel, and 2.) Use a ship with blind fire. You can use guided missiles sometimes, but I advise against it, because even with Hawks and Raptors it takes quite a long time to lock up and hit the target, sometimes you don't have that extra two seconds.

Oh, and don't get too close to torps either. Very easy to destroy yourself.