They tend to be found under floating objects where baitfish will seek shelter. Sometimes very large schools will hang in wait under these objects, I’ve fished for them hanging under all types of things from, weed patches, floating shark buoys , picnic tables to dead whales. While out on the water always try a few casts to anything you find floating on the surface, and I mean anything. One time we found a large school parked under a floating piece of 2 by 4 lumber.
The best method is to find any floating object and throw a few live sardines near it, if fish are in the area they will come up to feed on them. When you find them with this method you can hold them near the boat as long as you keep feeding them more sardines. When fishing like this I keep a rod set up with a standard unweighted sardine pattern and one with a popper in the same size and color pattern. Most times they will take the sunken pattern but at times they are selective or have been fished over and a popper works best. With a popper you make a surface commotion and show them less of the fly. And when you chum fish up with sardines and Dorado are in hot pursuit, the sardines tend to be in flight racing away on the surface much the same way a popper looks skidding along the surface.
Once hooked , the practice of keeping one hooked fish in the water will bring the whole school right behind the boat. The visual sight of these fish all lit -up is awesome. By using this technique you can get a number of casts into the fish and your chances for a hookup is good. The more fish the better, the competition factor always plays in our favor. They are great fighters, they run , jump and sound.