you need to do camera and lens correction firstly. In this question, let us focus on the basic panel. This is my work flow and the reason just for reference:
Reduce the contrast to -50. This is for flatting the 'gamma' to linear (stated in Real World Camera Raw). For a high-contrast image, it will help us to customize the black&white point as well as the details.
Adjust the 'exposure'. Low/High-key image corresponds to different exposure, hence, the histogram will stack on the left or right respectively. No histogram is always correct. The exposure slider is very important to adjust the overall key of image. You can adjust it beyond this step because it can provides additional headroom for shadow or highlight adjustment.
Black and White sliders. These two slider are similar to adjust the white or black clip by curves ( merely roll-off but not hard clip). If you wants to maximize the overall contrast, pushing the sliders as much as possible. During this step, you will find that it is very hard to maintain the details. Don't worry, we'll recover them in the next step.
While the black and white sliders killing too much details, using 'shadow' and 'highlight' sliders to recover the details.
The algorithem of this two sliders is beyond the tone curve and with the local contrast enhancement.
For your question, you need to know, 'too dark' may caused by either wrong exposure or detail-less shadow. Therefore, adjusting the balance between 'shadow' and Black clips.
Your purpose should be balancing the tone vs. details of shadows, so only these two sliders are not subtle enough, so you can allocate the tones by curves.
In fact the whole basic panel should paticipate in the process of balance. But I have told the mechanism of these sliders. The highest purpose of using each tool is balancing the details (highlight/shadow sliders) and tones (other tools including curves).
Finally, observing the tone between each part in image, if you can not find a balance for overall scene, you may be better to realize the local adjustment is necessary, by brush or other tools.
Apologize for my poor english : )