MT is dead on. get rid of the lateral line, all the brown stuff, and any white skin areas. i dont like the lower belly meat area, to me that is the WORST part. i always rinse my fillets in cold water also, using my hands to 'scrub' them. getting all of the oils/slime/scales/blood off.

i suspect that the fishy tasting ones are the pike. i ALWAYS clean my knife between filleting and skinning. pike have the worst slime (moreso in winter) and that has a really bad fishy taste. making sure you dont run a dirty(slimey) knife through clean meat is important.

ive never soaked my fish in anything, and only freeze them in plain water. ive heard that soaking fish in milk, saltwater, and some weird vinegar mixture (italian dressing has this so it makes sense) help to remove the fishy taste.