Asking "When should I throw a certain kind of lure?" is like asking "Why to baseball teams lose games?". There are so many factors that could lead to an effective/ineffective day throwing topwater. I will do my best to try and answer this.
If you see bunker in the water, yet they arent busting the water too much and are just breaking the surface here and there, well there are a few possibilities. The first most obvious one is, there aren?t any/many fish there. Even if there are a few bunker jumping here and there, it doesn?t mean squat. Bunker are about as smart as the moss that grows in your yard. They scare the crap out of each other, no kidding.
Second, the fish are hugging the bottom for whatever reason, be it boat traffic, non-aggressive conditions etc. If you see this, via flashes in the water, the most important thing to know is your depth. How deep is the area your fishing...are there any drop-offs off points or sandbars? This is a major factor to the key to your success. If the fish aren?t visibly busting, you have to find the level in which they may be holding.
Throw some shallow swimming plugs like redfins or javelins. Then throw some deep diving bombers. Finally buck tails and spoons.
Don't go for the maximum cast every time. Work in to out, increasing 20 feet each cast to that direction. This allows you to key even more to where the fish are holding. It allows you to present bait at even a better variety of depths. It also helps to keep from spooking fish holding behind your cast.
If this doesn?t work, then try the poppers...what do you have to lose? I personally throw a popper first when I hit the water every time. It?s loud and obnoxious, and if the fish are aggressive they will tell me that they are there. I don?t give them much time though. If something is going to hit a popper, he?s gonna do it within 5-10 minutes. Vary speeds also. Bluefish love hauled in lures. Sometimes bass prefer slowed down retrievals with sporadic popping.
Okay, now if you see fish busting on the water. Do you know what kind of fish they are? Are they bluefish? Are they bass? Try and figure that out. Also figure out what they are taking. Sometimes you can throw a piece of wood into a busting school and you'll nail the fish. Other times you'll be in a pool of busting fish getting splashed in the face, and not get a hit.
Why is this? The most important thing I keep stressing, comes from an old fly fishing proverb "match the hatch". Meaning if your fishing and you see pencil fish...Throw on a pencil popper. Rainfish/Spearing? throw on smaller sized whiter finished lures. Bunker? Throw on your 2 oz Gibs Polaris with the black top black dot on the sides. If still no luck theres one final possibility, your bait is outnumbered by 40,000 bunker or 1 million spearing and he don?t care whether he is going after yours or the one right beside it. It?s the luck of the draw.
If you see the fish are bluefish, just throw out your nearly paint-less chomped on poppers and hold on. Bluefish are not often picky at all, and they are gonna mess up your 15 dollar yozuri's

.
Other good times to use a topwater lure whether it is a popper, or a top water swimmer is when the waters are murky, such as after a rainstorm. Fish eyesight is good, but it?s not THAT good. If you can?t see your thighs while wading, chances are fish don?t see your lure 5 feet away. They more so go on instinct and vibrations. If you present a topwater lure, its gives the fish alot more to shoot for. If the water is murky then try lighter colored lures. If the conditions provide sunshine, try something with a chrome fish.
Hmm.Thats about all i got for now. Any other questions feel free to ask.