The most important part of fishing is presentation. The best presentation will always lead to a bite if the fish are present. The best presentation today may not be the best presentation tomorrow. Therefore, when the fish aren't biting you must adjust. Yes, the options are endless but you must start somewhere. Try changing colors, size, position, speed and so forth. You have to give the fish what they want where they want it. For example, you shouldn't present your bait on the bottom if the fish you're targeting don't feed on the bottom.
Gamefish are cautious yet opportunistic, especially if they sense a weakness. One of the best indicators of weakness in a baitfish is the retreat. A bait that is swiming away or having a difficult time keeping up with the main school is a great attractor and will normally trigger an attack. This explains why some umbrella rigs have longer trailers. This also works for bottom fishing, moving or jiggling your bait occasionally can trigger a bite.
Another indicator of weakness is size. Smaller baits are less intimidating. As a general rule, small baits will catch more fish while larger baits will usually catch bigger fish. We cant emphasize the word "general" enough here since there have been a number of big fish caught on smaller baits. As mentioned in one of our previous tips, bait color is important. You have to find the color that the fish want at the time you are fishing, so change is good.