From a boat, look for diving sterretjies, and cast spoons or plugs underneath them. If the fish are on the surface, simply throw your lure of choice in the middle or edges of the school. Do not race at the school, creep up ahead of them with your motors just above idle.
If you see other boats casting at the same school, be considerate of their position and do not under any circumstances troll through a school that other fisherman are spinning at.
Alternatively troll rapalas on rod and reel and squids on bungee cord behind the boat in the prop wash in the areas where fish have been found. Once you hook up, turn the boat a quarter to the windward side and throw a plug and spin towards the hooked fish.
Lastly look on boatfishing.co.za for the dummies guide. As for shore fishing, best you get the cliff fishermen to comment.