Focus: Auto, Pre, Manual & Continuous, Oh My!
If you have your camera on any sort of automatic focus, it's going to take a bit longer to shoot because the camera has to puzzle out what focus to put it on. This is usually the biggest cause of excessive shutter lag.
The obvious solution is to simply go into manual focus mode—though adjusting the focus might take as much time as the shutter lag. If you're planning on taking multiple shots at about the same focus, or are particularly quick about adjusting, you might want to consider manually focusing the camera to reduce shutter lag.
If you still want to keep it in autofocus, try another trick: right before you actually want to take the shot, try depressing the shutter button about halfway. Doing this, your camera will focus itself, completely poised to take the shot as soon as you press the shutter button down the rest of the way. This is known as prefocus. More information and tips on this technique can be found here.
Some cameras have a sort of dynamic or continuous focus, a compromise between auto and manual. As with the previous, you half depress the shutter button—but the camera will continue to adjust the focus on whatever object you focused on, even when it's moving closer to or further away from the lens. This isn't a universal feature and will likely need to be enabled, so consult your camera user manual to see if this is available on your camera.