There is photography and there is digital photography.
Move in close, off centred, correct focus and exposure for subject, etc are all basics in photography.
Digital only starts when we talk processing: where it was once chemistry, it is now algorithms.
If you are the type that just want to "get it right" at capture, and as far as you are concerned the processing is a "black box", be this "black box" your corner film lab or the processor in your digicam, then there is really no necessity to distinguish digital photography at all, but just photography.
And the only skill or secret you need to acquire is to learn to adjust your eye to see what your camera sees, or alternatively you and your equipment mutually adapt - to the extent possible - to give you the look that you seek, always holding the image processing a constant black box.
Not that this is wrong or bad. It is mostly practical, then in the days of film photography, and also now for those for which the camera is just another recording device even as pen on paper is.
But if you are the type for which the capture is only necessary but not sufficient to make a photograph, and the processing - chemical or algorithmic - is as much and as essential a part of the picture making process, then a world of difference opens up.
And then "get it right" takes on a different meaning altogether, namely "right" for what?
Where once it was "right" if it comes out as you like it after your "black box", ie "right" as it is optimised for your "black box", now "right" can possibly means what gives you the most flexibility in its processing.
Whatever it is, your notion of "right" will then shape how you capture in the first place.
So the secrets of digital photography are those additional or different things apart from essential photography that facilitates the "optimal" exploitation of digital capture and processing to make the "best" pictures.
And in this context the most important secret is what I called "maximal data at capture".
And this is aided by the histogram. The broader and fuller the histogram, without clipping or spiking at the highlights and shadows, means greater tonal data is captured.
Sometimes doing so make the picture look washed out in the preview screen, but you must learn to visualise the picture as the outcome of a combined process of capture and processing. Then I think we have started doing digital photography.
(In fact it is also the same for film photography, but with different tools.)