Since the words usually used for different techniques in spearfishing are the Italian ones, I wanted to make a list of these, with short meanings, and let everyone discuss the different parts and how to best accomplish them.
La Caduta: The fall. This is sighting the fish on the fall(or from the surface depending on depth) and pursuing it without it feeling like it is being preyed upon.
In Tana: In the Hole. Falling quietly looking for possible holes/lairs that might hold fish. Quietly(this is key) searching in the chosen hole an deciding if anything is spearable, or immediately(if still with air) looking around for other possible holes.
Aspetto: Wait. The breath up here is very important. The decent shall be with minimal effort. While falling(leaf like) look for a void in the rocks/bottom etc. or some cover. Once on the bottom extend your gun and assume a very stealth position and "Wait" for prey to come. There are many techniques to raise the curiosity of the fish, so this I will let all discuss.
Aggauto: Ambush. This is the most improvised of all. It is based more on instinct and improvisation than anything else. The key here is to anticipate the fishes next move. If a slow moving fish is spotted on the drop you could glide slowly as to fall behind it and shoot. If said fish starts to move away, a change of direction is needed, as to go away from it and intercept it. With this technique chumming can be used to attract the fish. The key here is to use cover, move slowly, silently, and calmly.
For the Italian speaking spearos here, please help with translation and or add others. With the more experienced, please elaborate and help the rest of us with more effective ways of hunting. Gracias.