When adjusting the three components of exposure you should be aware that each one affects your photos in other ways, which may not always be desirable:
Shutter speed - If your shutter speed is too slow your photo may blur, either from movement of the camera or movement of the subject.
Aperture - A wide aperture produces a narrow depth of field, so if you make it too wide you may have trouble keeping everything in focus. On the other hand, a narrow depth of field can help to isolate the subject, and is often something that you want; if so, you need to avoid using a narrow aperture.
ISO speed - The more you increase your camera's ISO, the more digital noise your photos will exhibit. This can make your image look grainy and reduce its sharpness.
As with everything in photography, adjusting these three settings is a balancing act. You need to decide what effects you want in your shot and choose settings that will produce them while minimising the potential downsides. Exposure stops are a really useful tool for doing this, helping you swap settings around with ease and giving you more control over your scene.