Trolling is fishing while towing your bait or lure behind a moving boat.  Trolling varies widely in practice depending on the species you’re trying to catch and what bait or lures you are using.  Trolling has a number of different techniques to choose from.  Here are a few of the major kinds of trolling and some of their uses:

Outriggers- These are basically long swing arms you see mounted on large sport fishing boats.  The goal of the outriggers is to hold lures out wide behind the boat as it pulls them through the water.  Some of the fish that are taken using outriggers are large bill fish and tuna, as well as certain species of sharks.

Down-riggers- The main use for down-riggers is to troll with lures at a deep depth.  The riggers have heavy line connected to heavy weights and small clips.  The lure is connected to a regular fishing pole and then clipped to the down rigger weight and lowered to the desired depth.  When a fish takes the hook the line disconnects from the clip and the angler can fight the fish as he normally would.  Mainly these are used for deep water fish like haddock, cod and some types of salmon.

Surface trolling- The most basic kind of trolling is done by dragging a lure behind a moving boat.  Some types of lures are made to skip along the surface of the water to draw in fish, others move smoothly a few feet down.  This depends on the lure action and the type of fish being targeted.

As you can see trolling can be used for many different situations.  Because there are so many options it is good to talk to people in the area about what they are using and how they are using it.  Being a successful fisherman is about talking to people, trying new things and seeing what works.