Watching your shadows and highlights is easier with this tool in Camera Raw. (Lightroom also has this tool).
To turn it on in Adobe Camera Raw, select the keys O and U to turn on the warnings. U is for Shadows and O is for Highlights. If you are clipping any shadows, it will turn those areas blue. If you are blowing any highlights, it will turn those areas red. You can also turn it on, but physically selectding the white or black triangles.
Here I have an image where I have the warnings off. To the naked eye, it can be hard to tell if I have clipped any blacks or blown any highlights.
I then have the same image where I have turned the warnings on. Where I see black and red, is telling me that the shadows are so dark or the highlights are so bright, that there is no detail in those parts.
Having some areas that are clipped or blown, are sometimes inevitable and do not affect the overall image. However, in things like wedding dresses and such, you don't want to have blown areas on a dress.
If you want to watch the clipped or blown areas as you adjust the exposure or blacks and such, hold down the Option/Alt button while you adjust the exposure, and it will show you those areas.