When shooting, you can use aperture priority, shutter priority, or go fully manual. In the former, you control how wide the aperture is, and the camera automatically sets the shutter speed; in the latter, you set the shutter speed and the camera sets the aperture.

Controlling the shutter speed lets you freeze an image or create blur; but that's not necessary in most shots. Instead, use aperture priority. Larger aperture values give greater depth of field, while smaller aperture values keep your subject sharp while softening, or even completely blurring the background. In many cases, this can help you achieve the composition you want, either emphasizing an individual element or showing a series of elements across depth. This is what you most often wish to do in your image.

So shoot using aperture priority. The setting is usually something like A or Av.