When setting up to troll for saltwater or large freshwater species try using the "tripper" rubberband. Once lure is dropped back to desired distance from boat, simply bring line straight down pole to area near handle of reel.
At that point attach a rubberband to line and loop to handle of reel. Advantage is this- Once fish strikes lure rubberband tripper will break allowing lure to fall back on fish. This in turn allows fish to complete strike most times. Should fish drop lure, more often than not, the split second fall of the lure will appear as an injured bait fish resulting in second strike. You won't believe the slamming strikes you'll get.
When trolling for fish and nothing seems to be biting, try changing lure colors and techniques. Sometimes aggressive fish like the lures right behind the boat. Boat-shy fish will often only grab a lure that is set back further. Changing trolling speeds and depths also have effects. Nothing ever works good consistantley. The behavior patterns of fish can change daily and even throughout the day.