if your camera has an autofocus, hold the shutter button halfway down for a second so that the camera can check it's white balance (if it does that) and focus on the subject. This is even more important if your camera has a multi-point AIAF, where you have to check if it's focusing on the right spot.
Otherwise, if you push it down really fast, it has to calcualte white balance and autofocus before it shoots, making the shot delayed.
I mistakenly set my camera for 1 second shutter speed during the second half the build period and didn't check it until after we shipped. Needless to say, I have cool, albeit REALLY BLURRY pictures
